I love using Easy Fancybox to create popups in lightboxes, and it’s especially nice when you use it to play a video from clicking an image or text link. Here’s how you do it:
1) Install the free plugin from the WordPress depository.
2) Add this code where you want an image to link to a video:
Of course, you will replace https://youtubelink.com with your actual youtube link and then add those extra characters on the end.
And you will replace http://www.yoursite.com/wp-content/uploads/your-image.jpg with the URL for your image.
If you want to use a text link instead, follow the instructions above, but replace the image code with your link:
Hope this is useful to you!