Board Thread:Support Requests - Getting Started/@comment-26415383-20151003222619

So I was recently give admin rights to a wiki and I need a bit help with linking. I read over the whole page but not in one part did it mention putting a link in an image. On a wiki I like to use called Steven Universe wiki when you are on the home page and hover over the image of main characters you can go directly to the link, so how can you add the link into the image so it is hidden but only appears when hovered over? I couldn't find how to in any guides. 