Hi, welcome to the forum buddy. K2's are the best, i had one a while ago - lovely machine. Mine was a K2 silver curvy.. as everyone knows they are the best AND the fastest.
To add an avtar you need to go into your profile option at the top..
Somewhere near the bottom there is an "add avtar section". the image you upload needs to be no more than 150x150 i beleive, just click the browse option, select the image you want from your computer, the hit save.
HTH.
Enjoy your time here buddy.
GYKD.