Maybe you should read more careful next time, as the answer you're looking for was right next to you.
Q. How do I get pictures into my signature?
A. First you will need the image you want hosted on the internet. You can use Imageshack (you don't have to sign-up for this), or you can use Photobucket (you have to sign-up, but it's better if you're uploading a lot of images).
Once you do, it's simple (remove the stars):
Normal image: [*img]url of image[*/img]
Image linking to a site/thread: [*url=url of site/thread][*img]url of image[*/img][*/url]
Side note: to create your own great looking signature images, try this guide