A lot of people here ask this question...so I have an answer for you!
Okay so we're kind of starting from square one so I'm gonna throw a whole lot of information at you. I hope it makes sense.
Good to know: The small pic under your name is called an avatar

or avvy for short
Where do you go? To upload an avatar, or update your signature click on "Profile" in the menu at the top of the forum page.
How do I get graphics? If you would like your own personlized banners or avatars go to the
Requests section of the forum and ask someone to make something for you.
Any other way? You can simply click on "Show Gallery" in your Avatar Control Panel (found at the bottom of your profile page) and choose one of the pre-made avvys.
URLS: To learn how to put pics into your sig it's important that you understand URLs
~So lets say you asked me to make you a banner at my request thread. You wait, I make it yada yada yada. So now it's posted. To put it in your signature you could
-Use the URL I gave you. So right click on the image click "properties" and you'll find the url. Copy it and paste it inbetween [img]and[/img]
So [img]URLofpicHERE[/img]
That is what you put into your signature box which you will find in your profile.
A smart idea: Upload banners for your signature onto your own server. Why? Because some people ask that you don't use the urls they give you because they'll be deleted the graphics from their own account soon...and it's easier to keep track of all of your graphics when they're all saved to one place.
How to do this:
1. Save your banners/avatars on your computer.
2. I reccommend
www.photobucket.com as a good image hosting site.
3. Go there and make an account. (you'll need an e-mail address)
4. Upload your images onto your photobucket album. Your image will be given a URL. Now photobucket will give you the code with your url, so just copy the url in the
img box (under url and tag) and paste it into your signature.
~To upload your own Avatar, you can upload it from your computer. Just go to your Avatar Control Panel and click "Browse". Or you can give your avvy a URL through photobucket and enter it into the "Upload Avatar from a URL" space.
I hope this made some kind of sense. If you need any more help feel free to ask.