In order to embed web-based videos like YouTube videos in your presentations in PowerPoint 2016 for Mac, you'll need to install an Add-in for Office. Here's how:
Select the Insert tab on the ribbon, and then select Store .
Enter 'Web Video Player' in the search box, and follow the steps to install the Add-in.
Once the Add-in is installed, you'll be able to use it to play videos from YouTube or Vimeo directly in your slides.