From the FAQ:

How do I change my avatar/image?
From your Profile Page, click 'Edit' from the top menu and then click 'Update Your Image'. From here you can either select an image from our gallery or upload your own. Your own image must be no bigger than 500 KB – it will be resized automatically as needed. Click 'Browse' to select the image from your file system and click 'Upload' to send it to our site.

You can also add photos to your photo gallery - to do that, click on the 'My Photo Gallery' tab and upload the photos there. (This info about the photo gallery isn't in the FAQ yet - I need to update it still, sorry!)

Hope this helps. If not, let me know!