There's a sort of frame around the radar picture. On the bottom of the frame, one of the options says something like "loop of this image." Click on that, and you'll get a loop of the last hour or so of the most recent images.
Hubby's a landscaper, I go to the weather radar almost as often as this forum!!
If you are already looking at the local radar picture, click on the "composite, loop" option in the column on the left-hand side of the screen.