How do you change your avatar?

It escapes me how to do it, and I can't find anything in the help section. Maybe it is only possible for paying members?

Hi, You can send it to us via email regardless of whether or not you're a subscriber. The size required for the forum is 50 pixels square, so bear that in mind if you are sending in something bigger which when reduced results in something that isn't very clear.
flopsy