NOTE: These instructions have changed. It is now much easier to add a video to a post.

YOUTUBE
If your video comes from YouTube, simply pasted the URL into your post, like this:

Voila!

Here’s what that looks like in WordPress:

VIMEO
If your video is from Vimeo, paste the URL in this format:

Which will appear like this:

USING EMBED CODES:
You can always use the embed code for any video as well, but you must click on the HTML tab in the upper-right corner of the WordPress field where you are entering your content. It will look something like this:

And NOT like this: