PowerPoint®

I am working on a PowerPoint® presentation and I need some help. I have a graphic that I have inserted into my presentation. The 'background' in my picture is white. Does anyone know how to make the white background transparent without making the contents of the picture transparent? My presentation color scheme does not include white and I think it looks kind of silly when I have a nice presentation and then all of a sudden I have a picture that is obviously imported.

Thanks for your help,
Hopper