Alright well, first of all, once you have the picture you want, it has to be less than 400x400. I don't know how much you know about pictures, so I'll post all the instructions.
Once you have the picture, left click on it, and click on 'properties' at the bottom. A box will appear. There will a bunch of information about it. One of them will be how big the picture is(it'll be like, 304x500 or something) so if it is less than 400x400 you can use it. Then you have to find the code for the picture. It will be like a website format and end in .jpg. High light that code and put it in your signature(to put something in you signature, click on 'register' then 'edit profile' and then if you scroll down there will be a box that says signature and put it in there) after you paste the code, surround it with
so it will look like this -
then press save changed at the bottom of the page and it'll be there. Also, if you want to put a picture from say your digital camera not from a website, you have to upload it to a picture sight and then follow the directions to find the code.
If you don't get it reading all this(I wouldn't blame you, I'm not very good at giving directions) ask for help from Dan Murphy or post a thread on the tech board and they'll explain it better. Hope I helped!