Yes, a signature is a pic below your message (Mine says Hermione Fan and Marstar.)
A good place to find pictures is here:
http://www.glitter-graphics.com/I like the funny pics.
So, find a picture you like.
Click on it.
Find the BB code.
It will say the following:
To post on Glitter-Graphics.com and forums, use this BB code:
Copy and paste the code onto the signature part of your profile on this website.
(Go to Profile, Then signatures. Paste the code on the space given.)
Then click on save.
Then go to Prefrences (It is in your profile part of the forum.)
Find the sentence "Always attach my signature :".
Click on yes.
From now on your posts will have the picture below it.
If you still need help, PM, email or post here what you don't understand.