You have to put in the comments of one page the picture of the other.
For that, depending on the browser, you have to retrieve the image address (often in the menu appearing when right-clicking on the picture).
That image can be pasted in the second field of the "Add picture to comment" tool. Otherwise you can also save locally the picture and submit it like one of yours, but it is one more step.
Usually we keep the oldest page or the one with the highest rating as "main page", and we put in comments the additional (lower rating) ones.
If there are interesting comments you can "move" them by quoting them on the source page, copy the block in the "add comment" area, and pasting it to the comment area of the target page.
Once all useful info is on the target page, the source page can be deleted.