Welcome to PT! If you go to my account you will find a link there that will take you to the road guide for the site.
As far as custom avatars are concerned; when you reach "Friend" status (50 posts in the forum) you send your 70 x 70 pixal avatar to Taz@planet-tolkien.com and he will put it up for you. Once it is there, if you make any changes to your account, then the avatar will delete and you will have to contact Taz to have it loaded again.
I look forward to seeing you around. And if you get a chance, drop into the chatroom.