How do you move collections around?

I haven't been able to figure this out, I have a lot of collections and I want them to appear in alphabetical order, however I don't know how to reorder from what they currently are.

I understand the answer is probably obvious, but I have googled around and spent quite some time on this and I just cant get how you are supposed to do it? (I have tried on both mobile and browser, just in case)