How do I set a custom avatar?

Sorry for the dumb question, but how to I set a custom avatar picture and what is the max size?

I can only seem to select from the six avatars included with this forum.

If you ever find out, let me know because I have the same "dumb" question. I believe the answer is that it is an option for the forum that has to be turned on or of by the Moderator but that is just what I have found in other forum's and may not pertain to this one.

Please post if you find out though, I would also like to use my avatar.

AW