LOL, don't worry, Lolly - no question is too dumb here. We've all been there. Personally, I have the technological capacity of a wombat with a lobotomy. The first time I tried choosing an avatar, I kept forgetting to update profile at the end, so naturally enough none of the changes I made 'took'. Took me days to figure out where I was going wrong.
Okay, what you do is: Choose the avatar you want to use. Put the pointer of your mouse over it. Right-click, then click on 'properties'. You see that bit that starts 'http'? That's the url (the location on the internet where you can find it) of the avatar. Copy that. (Just do the same thing - pointer, highlight the url, right-click, choose 'copy')
When you get to the bit in the profile that requires to you put something into the url section - just click on the box there, rightclick and choose 'paste' (or you can hold down ctrl and v on your keyboard at the same time and that will do the same thing) and the http url should appear in the box.
If you hit any other glitches, just ask!
LabRat