I know I've learned this before. I don't usually use it on audio, but I tried today and it was a mess. I had someone with me and I just wanted to create a quick repetition of me playing a part for him to play over.
 
duh... I know, rtfm. I tried Help and have spent a bit looking. I know peeps here know it right off.
 
Could you humor me and just tell me?

Go to the Groove Clip section of Clip properties in the Track Inspector, and correct the Beats in Clip value. Then drag it back out to the original length and you'll see it start repeating at the point.