A new feature in OneNote for Mac is embedding third party videos into a OneNote page via OS X’s Share Extension. Note that this feature is only available on apps using the Share Extension.
To embed a YouTube video using Safari, click on the Share icon, then click OneNote. If OneNote is not listed you may need to add it by clicking More and checking OneNote.
Once you’ve clicked on OneNote, the Share Extension popup will appear to enter a title, a description, and to select the notebook the page should be added to. To select a notebook, click on the dropdown box on the bottom left side of the popup window. From there you will be able to select the Notebook and Tab to add the new page.
Once you’ve clicked Send, a new page will be created in OneNote with the embedded video.