once you go to your 'mibba' go to your 'gallery' and when you upload a photo it asks you do you want to use this as your profile picture and all you have to di is click the box.
click on 'my mibba' and the go to 'profile' and then click on 'CSS' and then there should be a link you can click to go to the pre made layouts and then you can pick anyone the have... :) hope that helps