Here you go:

Thread: HOW-TO: How to Embed a video to GLP.

Regarding embedding images. You have to be a paid member to directly post/embed your own images. Otherwise you can only choose from the site hosted images at the bottom of where you type your posts....

If you want to share images as an A/C you will have to upload them to a 3rd party hosting website like photobucket or imageshack and then you can post the URL (link) in your posts.