Lost with this new task..please help.

I am not at all saavy to gallery or php. It took me forever to install my gallery and change the simple colors and things the way I wanted them.

My gallery is used in conjunction with a basic php forum and is used for the members-photographers and models- to display a small personal gallery of thier work. I currently just have a link to the members gallery. ( http://www.lastingphoto.com/gallery/ )I am revamping the site and adding a lot of things. I want to have a table on the domains index page that has an advertisement to visit the members gallery with an image from the gallery set to randomly show images from the all the albums. The index page will be a basic html page.

I don't have a clue how to imbed this..can anyone point me in EASY to understand directions or give me a generic code where I can just change the info to my specific gallery. I am probably WAAY over simplifying this as I assume there is changes needed in my gallery files also?
Please help.
Thank you so much.
Vic