You can currently use one of the forum avatars. Click on UserCP Just below the Islamicboard.com LOGO up top. Then click user options and when that page comes up, scroll down on the menu to edit avatar. Until you become a full member, you can only use our stock avatars that you can browse through.
You do a signature in a very similar manner. but you will not have that option until after you become a full member.
You become a full member by posting 50 meaningful posts.
Welcome to the forums. Look around get a feel for the place and read the FAQs.