Impose - hover text that links in galleries


Hi there, I’ve just set up a new website with a gallery. At the moment I’ve set up each image in the gallery to link to other websites. But I’d really like hover text over each image that links. I have tried to install plug-ins but can’t get it to work. I don’t understand where to put the code in. Any advice would be great! Here’s the page so you have an idea what I mean. I want the hover text to be a caption (e.g. film review, Saturday Paper) that then links to article in new tab.