An "avatar" is much like an identification image... a picture. Here's how to put up you own:
1. Click "Profile" located at the top portion of the page, right below the forum's title "NSEC IV-1 Batch '97)
2. This section allows you to change your registration details as well as give you some other options including putting your own avatar, on the upper right portion, you'll see the option "Avatar" (pink arrow), click this.
3. You have several choices where you can upload your avatar. It can be done
a. directly from your computer
b. upload from a URL (web address)
c. link to offsite avatar
The last options are only applicable if you uploaded your picture from photo-hosting sites like Flickr, Photobucket, etc... It works very much like in Friendster. This technique is also used when you want to place pictures for your post.
4. Click "Browse" (in red circle) if you're picture is from your computer or place the URL in the box/es if you choose option b or c
5. Click save and your done!
Hope this helps!
Cheers!