You can add video links from websites like Youtube to your PowerPoint presentations.  To do so:

1. In your web browser, locate the video you want.

2. Copy the URL of the web page from the Address bar of your browser.

3. Switch to PowerPoint and select the slide where you want to place the video.

4. On the Insert tab of the ribbon, in the Media group at the right end, select Video. Then select Online Movie.

5. In the dialog box, paste the URL you copied in step 2.

6. Click Insert. The video is added to the slide.

7. To preview the video, click the Play button that appears on top of video.