You don't need to feel thick Chanski - it's not all that obvious.
Near the top of the screen there is a row of tabs, starting with "Home". Click on "Profile". On the resulting page, there are some options down the left hand side of the screen. Under the heading "Modify Profile", click on "Forum Profile Information". Then you will see some options for adding a picture.
- If the picture you want to use is already on the Web somewhere and you have an Internet address for it, select "I have my own pic" and enter the URL address in the field opposite.
- If the picture you want to use is on your own computer, select "I will upload my own picture" and press the Browse button. Then you can navigate to the right directory and select the file name of your picture. When you've got it, press the "Open" button and the file path should be shown. (None of the directory information is actually transmitted - this is just used by your browser to identify the file).
Then when you've identified the picture, scroll right down to the bottom of the form and click "Change Profile". If you're uploading a picture from your computer, it will take a little time. (Don't use a file that's really huge, say more than 100K, because it will take a long time, and may be rejected in the end anyway. But the picture itself can be any size or shape - the forum software will resize it to fit.)
Once you've done all this there should be a picture attached to your profile, and shown on every message you send. If you don't like it, or get sick of it after a while, you can change it by repeating the above steps.
Good luck!