Both phrases are understandable. The first phrase is literally telling someone to hover over the images so that they can view the content. If this is not your intent (maybe because the content will not be viewed easily), then the second phrase would be better. The second phrase, to me, is saying to click on the image in order to view it. Really it depends on the effect you are actually going for (hover to view/click to view) and which option you think let's people view the content the best. Let me know if this makes sense or not.