How do you customize your profile, and how do you change your avatar???
well, at your profile page is a buttom with 'change theme' on the right side and another buttom with 'change avatar'. Also if you click on the buttom info on the left side, you can click on 'edit profile info' where you can write about yourself. If you want a picture as background :Pick a picture, save it, go to 'change avatar', click on pick it, choose your pic, click on upload, then you get a link, copy that a put it on the bar by background :)
Hope i have help you ;)
first have to at least go to profile settings and do anything you want