Installed Ubuntu 12.04.2 on my laptop. Need help w/ Steam

As stated in the title, I just installed Ubuntu 12.04.2 on a separate partition on my laptop. I got everything as up to date as I could but when I started up Steam I got this error message:
"Steam needs to install these additional packages:
libgl1-mesa-dri-lts-quantal:i386, libgl1-mesa-glx-lts-quantal:i386
[sudo] password for (my user name):"

This is the first time I've messed with any form of Linux before but I figured it couldn't hurt to try it out. Does anyone here know what might be causing this? I know nothing about Linux. My laptop is an HP Pavilion DV7 6135dx. The graphics card in it is an AMD RadeonHD 6490M.

try manually installing one dependency or the other

-Close steam
-Open the program called Terminal or alt+f2 and search for terminal
-type:
sudo apt-get install libgl1-mesa-glx-lts-quantal
OR
sudo apt-get install libgl1-mesa-dri-lts-quantal
-It should ask for your password, don't worry if the cursor doesn't move, then press enter
-Stuff should download and install, if it doesn't, try the other line
-Try steam again

One question: How exactly do I close Steam in the first place? I can't seem to figure that out.

Just close all steam related windows, error boxes, and terminals. I think that should do it. I think there should also be a steam icon in the unity launcher. In the event that its stuck, you can force close it by running
sudo killall steam

It said no process found.

well, then, I suppose its closed. proceed to install your dependency.

Yeah, I don't know if its working yet. There's a question mark icon labelled Steam and if I right click it the usual Steam options pop up but the Steam interface doesn't show up.

I am not in the position currently to reproduce your errors, so I'll link you to 2 sources I've skimmed through:
First, the steam page on ubuntu wiki, which lists a bunch of procedures you have to do in order to get steam running

Second, people have been getting your problems related to 12.04.2 and have had success using different solutions on the steam website. Most of the instructions are copying lines of code into the terminal, so it shouldn't be too hard.

I just gave up and installed 12.10. Now it's actually working. However the first time I ran steam it also gave this long error message:

"You are missing the following 32-bit libraries, and Steam may not run:
libXrandr.so.2
libpangoft2-1.0.so.0
libpango-1.0.so.0
libfreetype.so.6
libfontconfig.so.1
libgobject-2.0.so.0
libglib-2.0.so.0
libgtk-x11-2.0.so.0
libgtk-x11-2.0.so.0
libgdk-x11-2.0.so.0
libpangocairo-1.0.so.0
libgdk_pixbuf-2.0.so.0
libcairo.so.2
libpango-1.0.so.0
libfreetype.so.6
libfontconfig.so.1
libgobject-2.0.so.0
libglib-2.0.so.0
libXi.so.6
libasound.so.2
libXrender.so.1
libnss3.so
libnssutil3.so
libsmime3.so
libplc4.so
libnspr4.so
libdbus-1.so.3
libpng12.so.0
libcups.so.2
libgcrypt.so.11"

Fortunately, Steam is actually working now.

I use Gentoo, and I expected a lot of error and be unable to run it... when i finally got the time to try it it was toooooo easy. just install the "emule-x86" packages. and it was done, download team fortress test it worked fine, just one issue with sound but i got the general idea how to fix it.

unfortunately Left4Dead is not yet available... well we will have to wait... i hope they add Zombie penguins by the time they release for Linux :P

Why would you need an official release? I haven't had a problem running & playing any of Valve's games using WINE.

because although Wine is capable of emulate a lot of Windows software components and API just fine. is definitely better to play a game that has been designed to use the naive library(on Linux that is). also there is a possibility that on a close future they release new AAA games for Linux... hopefully. thanks to valve initiative

it is near impossible to emulate games that use DirectX11-Direct3D libraries as DirectX is not available on Linux. for example i highly doubt that is possible to run Witcher2 on wine.

also Valve noticed that optimizing games for OpenGL and Linux is not a bad idea at all: Faster Zombies! on Linux (http://blogs.valvesoftware.com/linux/faster-zombies/)

http://appdb.winehq.org/objectManager.php?sClass=version&iId=23504

Oh look, Witcher 2, platinum compatibility.

Also:

Wine Is Not an Emulator (WINE)

The phrase "Wine Is Not an Emulator" is a reference to the fact that no processor code execution emulation occurs when running a Windows app under Wine. In Wine, the Windows app's compiled x86 code runs at full native speed on the computer's x86 processor, just as it does when running under Windows. And Windows API calls and services also are not emulated, but rather substituted with Linux equivalents (Ie. you don't need DirectX) that are compiled for x86 and run at full, native speed.

You should research more before you make unfounded statements.

Starcraft II also runs perfectly.

Thanks for enlight me.
I didn't know, when I try to install witcher 2 on Linux, long ago that was not possible. and i had a ton of errors... (and for what I read still apply to many users on Wine. also according to the records there "garbage" on 2 distros.. well that no good... ) also i will like to know to which level(high quality) is capable of running...
and Yes, I forget it is not actually an emulator per-SE.

now there is a problem on regards of DirectX yes wine Try's to replace directX with Open GL, and they way they handle that is nice, however nothing ensure that the speed will be the same. due differences on how directX and Open GL works.
some application may work event better than on windows some others might not.
also wine does not support DirectX11 as default, that might remove some feature of the game ( http://wiki.winehq.org/FAQ#head-fbaa851e07d7484640cc10b6d0c48abc741260b2 )
unfortunately this is due they cannot do a reverse engineering( as per Microsoft EULA is illegal ).
and wine is not good with copy protection, thanks now days more and more devs are reconsidering adding suck measures.
now don't get me wrong i don't dislike wine, on the contrary i love it. however the matter is i prefer a native option whenever available.

and wont you agree? if you could run PS3 binary one a computer and the game is also available for PC will you still go for the alternative rather than a native(of course assuming has the exact same content.)?

and as mention on my replay valve implementation of Left4Dead they have reached more performance optimizing a game for Linux than on windows( therefore even better than calling using wine.) Faster Zombies! on Linux (http://blogs.valvesoftware.com/linux/faster-zombies/)

and going on topic again. Steam on Linux is great, how knows maybe they can use some features of wine or call wine from Steam natively running on Linux. to run games that might not be available on Linux.