Apple users

i use a mac laptop, and i am having alot of trouble with all the downloads(except doujins, which work well). what should i do so that i can download all this good stuff onto my mac?

im using the most recent OS

when ever i download the RAR i open it up with Stufit expander and it loads or something and then it asks me to find the file or something, and nothing works. is stufit the wrong program, could you guys recomend another one

ps: sorry i couldnt post earlier