Same way you got the one you currently have. Control panel, armatars, choose one, save. Unless is isn't about armatars, but in that case your question needs to be clearer (and you might need to go read some stickies and the help page too).
Not currently, but if you go look in the AG3 forum, you will find at least one sticky that tells what the plans are for armatars in the next version of the site. I believe there has been talk about uploading your own armatars, but as it is, it will not be added at the launch of the new site.
