need help with how to make a popup-clickable index-image

Hello!

My buddy wants a page which gives the visitor a indexpicture (popup) with three choices. When the visitor clicks a link for that particular category that page loads, but there also needs to be a link to the other two sites/categories as well. Hope you understand what Im after here. Thought of categories but how to make the different menus show depending on what the visitor clicks on at the index-image? Im not a coder so I really need easy instructions ??

Thanks!

Dave