To change your avatar click on
Profile at the top of the page, and then on
Forum Profile Information (on the left in the
Modify Profile section).
From there you can either pick one of the many that come with the forum (
Personalized Picture), or upload your own from your computer's hard drive (
I will upload my own picture). Then click on
Change Profile at the bottom of the page.
To post pics you need to get yourself an account with a picture-hosting site such as Photobucket. This is free, and allows you host pics that can then be displayed here using the
Insert Image button, or getting the correct link directly from the photobucket controls.
Photobucket address (there are others, it's just the one I use):
http://photobucket.com/Once you have uploaded your image to Photobucket you then can click on the part that says "Image Code", which will copy the correct link you can then paste into your post.
The text you need to paste will look something like this:
[IMG]http://i2.photobucket.com/albums/y40/Plynkes/Borat2.jpg[/IMG]
And will appear on the forum as this:

Or you could become a Supporting Adventurer and then use the Lead Adventure gallery function.
Sorry if the explanation is a bit complicated and not at all clear. I did my best. Give it a try, and if it doesn't work just ask for help. Can't do any harm.