Changing profile picture

Hi! I just bought my first Mac, a 13.3" MBP with retina display. I am new to the Mac OS, so please bear with me...I scanned a photo of my wife and I to use as a profile picture, however, I cannot make it happen. I go to system preferences>Users & Groups>Click on profile picture and I can only choose from default, recent, or camera. If I click on "edit" there is no "choose" option, only the option to zoom in or out of the default picture.

The pictures are scanned as TIFF format if that matters, however, I did attempt with a JPEG as well with no success. The OS is specifically OS X 10.8.3 if that matters.

Also off topic, can anyone direct me to a video or tutorial of some sort for new Mac users to learn features? I'm not new to computers by anymeans, so I don't need something to tell me how to click a mouse, just stuff that past PC users probably wouldn't know.

Thanks!