Under avatar go to Profile at the top menu bar, and there is a secret place at the top of your profile in black lettering (doesn't look like a button but it is) that says "Modify Profile" Once you click that there will be a bunch of things that you can edit. Under avatar just upload a picture, or copy and paste the link to an online image. Then you have to type in your password at the top, then scroll to the bottom and hit save changes.
Same process for the banner almost. Create your banner however you would like and upload it to photobucket or facebook or something like that. Then (photobucket is easiest) copy the image source. It should look like this:
link here with no spaces [/img]
So you can just copy the image location and add the if you want. Be sure that the IMG is lower case. Paste that into the Signature part of your edit profile page, enter password, save.
Typically, signatures are measured in pixels. Some places like Photoshop have other measuring options, but it's better to stick with pixels if it's staying on the computer.
I think anything over 600 pixels wide and 200 pixels tall is a bit over the top. Of course, shorter siggies that are also taller aren't bad, either, as long as they aren't overwhelming. My siggies are typically 500x150
I found a web site that allows you the power to make banners, what I haven't found out is how to move the banner where ever I want, like hear. Dout they wanna chance me making one any way. 2cont thing not found out, how to add to a picture that I wanna use.