Remove the background of a picture on a slide

Select the picture with the background you want to remove.

On the Picture Format tab on the toolbar ribbon, select   Remove Background. 

PowerPoint immediately applies bright magenta to the background of the image.

Go to Background Removal > Mark Areas to Keep or Mark Areas to Remove.

Mark areas. When you're satisfied, select Keep Changes.

Select the picture with the background to remove.

On the Picture tab, select  ​​​​​​​Remove Background.