
Step 1: Click the "share" button below the video.

Step 2: Click the "embed" button to the left of the "email" button.

Step 3 (optional): Adjust the size that the video will appear in your post.

Step 4: Copy the embed code from the textbox.

Step 5: Paste into your post and select "click to configure post options"*

Step 6: Select "HTML On - Auto Linebreak Mode" from the drop-down menu.

Step 7: Monkey.

If your video is not on youtube look around for similar share and embed buttons on the video.
* this option does not appear if you are adding a "fast reply".