what do you mean? change your icon?

I'm not totally sure about the size, I think no more than 100 x 100? Idk, it may just have to be of perfectly square proportions. (Mine was
50x50 and they expanded it automatically)

But what you do is go to the MENU button right below your current icon, and then click "SETTINGS".
That'll automatically take you to 'general settings', where it should say something like...

My Name: -Text Box-
and then
Submit New Icon: -text box- Browse

Click on "Browse" and select the picture from your somputer that you want.
Then just click "Apply" at the bottom of the screen and your done.

So,
Menu > Settings > General Settings >
-(Submit New Icon) Browse
-Apply

And you're all done ^^