You can only embed Videos from Youtube.
Step 1: Getting the Youtube Video Link
In order to add a video just copy the Youtube Video URL from your Browsers Address Bar.
Step 2: Adding the Video
Paste the link in the following formats only:
In the Preview the Video will not get displayed but in the final published post it will show up fine.
If you edit an existing post make sure to click on “Edit” and then on “Go Advanced” before you add a video.