First find the YouTube video you want to insert. Note the channel and name of the video... OR you can copy the EMBED code.
In your powerpoint, on the slide where you want the video to be, click the Insert tab, and on the right you'll see Video. Choose "Video". You have the choice to search YouTube for your video, using the channel and video name, or you can paste the embed code.
You can't download videos from YouTube unless it's on your own channel, but using either the link of the video or the embed code will allow you to access it later.
Updated November 2015
