the picture by your name is called your avatar. to edit your avatar go to "User CP" on the top of the DISboards, near the "DIS Home", "Chat", "News", etc. Once you click on User CP, you will see a column on the left side that says "Control Panel", under that you will see, "Edit Signature", "Edit Email", etc., then you will see "Edit Avatar", click on edit avatar. From there you will get a page that shows a list of avatars you can choose from or you can upload one from your computer.
to do a signature, go to "User CP" like you did for your avatar. Click on "Edit Signature". Then you will see an area to put words, smilies, pictures, etc.
any other questions just ask.