Anyone know how to link pictures in your email signature to a website?

I am using Microsoft Entourage as my mail client for work on my Mac. I created a signature that I want to use but cannot link the pictures to different website. For example and I have a facebook logo, twitter logo, my blogs logo, and my LinkedIn logo in my signature but people cannot click on the logos to get to those web pages. Any ideas? I cannot seem to figure this one out.