Hi, I can't seem to find any way to upload an avatar? Is this limited to more established members? Thanks.

You have to go into your profile, and you'll see a space to post a link to your hosted avatar. It even specifies how large the avatar can be.

And the key word here is hosted. If you are trying to upload from your PC, that won't work. Your avatar image must be linked from a host (such as Photobucket) or from the library images available from the forum itself.