k here goes
click on the sealine map.
on the left hand side there is a block with a number of options, left click once on the "my account" option
look along the top and you will see a section that says avatar, left click once on it
in this section you will see a browse block, you can upload a picture from your computer as long as it is a jpg format and under a certain size, tells you how big. choose browse find picture on your machine and single left click it. then click upload.
if you want a sealine avatar, look at the bottom left hand corner and choose a catagory and highlight the one you want. click upload avatar added
hope this helps