How can I add an animated gif in PowerPoint?

To add an animated GIF to a PowerPoint presentation:

1. Search online for the appropriate GIF file that you are seeking. For example, you can do a search on Google Images for cat gif, then click on one so that it opens. 
2. Save the GIF to your computer by right clicking on it and choosing Save As. Make sure that it saves as a .gif file.
3. Open PowerPoint.
4. On the Slides tab in Normal view, click the slide in which you want to embed an animated GIF file.
5. Click on the Insert tab.
6. Click on Picture.
7. Browse your computer to find the GIF that you had previously saved. Click on GIF.
8. Click Insert.                       
9. Adjust size of your video if necessary by grabbing the corners of the video and stretch to desired size. 
10. Click on Slide Show tab, click Start from Beginning or Start from Current Slide to preview.

For further information, see:

Add an Animated GIF to a Slide

Add Animations to Slides

Inserting Videos

Inserting Pictures