Create a Simple Looping Animation

Pardon my incopetence -  I am trying to create a little looping animation where my character's legs each move in a circle without stopping. That's it. Just a constant unstopping circle walk. Like some other users, I don't want to use the Walk behavior because it's seemingly designed only for a very specific type of  tall, narrow humanoid body-type. My characters (being fat and short) consequently don't work with the Walk Behavior (unfortunately it seem like it was animated with such over-the-top exaggeration in the shoulders, that my characters will never look natural while using it).

So, I'm trying to just create a simple animated loop in the legs - the kind of fundamental thing we all did the first day or two of animation school. It's a task that would take maybe 10 seconds to do in After Effects, but I simply can't find this feature  in Character Animator.  I feel it must exist and I just can't find it. 

But as best as I can tell, the only way I've found to do this is to make an animation with keyframes, and then copy-paste them in my timeline over and over again to infinity, but the actual software doesn't seem to be able to figure out how to create this simple looping without me literally copying and pasting the loop manually. It's obviously difficult to accept that this is the case. So, I'm assuming I'm a dummy and missing something obvious here. Thanks for any help.