Really simple, actually! Once you have the links to all the pages you want to put in your signature, click on "Profile" at the top of the page.
Then click on Signature
After that, you just put in your coding however you want it. You should be able to look up HTML coding fairly easily, and there are buttons at the top of the text field that will help you out with basic coding scripts, but to do a link the script is:
[url=INSERT LINK HERE]Whatever Text You Want to be Clickable[/url]
And if you want to post an image, the script is:
[img]INSERT IMAGE URL HERE[/img]
Just make sure for the image you need the link to be directly to the image itself, not the page you found the image on. Usually you can get this link by right clicking on an image and selecting "View Image" and it should pull up a page where the only thing you see is the image itself. If you try to post an image and it's not working, you're probably just linking to the wrong place.
Hope that helps!