poop on the screen of your computer. INSTANTLY works and picks a picture of your liking for you by reading your mind!
nah im joking just go to >my account, than when your there on the left side itll say edit profile picture.
User CP edit profile picture, find a picture you want resize the pixels to 100 by 100 and there you go.
Just a note...your profile pic only shows up on your profile page...if you want to change the picture that appears appears in your posts, that's your avatar... Confusing the 2 is a common problem, so I just thought I'd mention it...