How do I replace the Ethan models?

For context: I'm a total Unity n00b. Actually, I'm a total game/graphics programming n00b. I'm a server-side programmer, but I have some ideas about things that I think Unity will work well for. There's probably lots you all know that I don't :)

One of my ideas is a "cheetah run" game for my cheetah-obsessed daughter. So I built up a simple game, and got all the details working, except that it's Ethan chasing a bunch of blobs. Not a cheetah chasing a bunch of antelopes. I downloaded this asset: https://www.assetstore.unity3d.com/en/#!/content/52040 and now want to replace the Ethan character with a running cheetah. I followed the instructions in the ThirdPersonController notes, but the cheetah in question doesn't animate at all. I've disabled its animator in favor of the TPC's, and I've made sure that the avatar in the TPC is set to the one in the package.

What sorts of things should I try to make this work? Or, will it not work because of some thing I don't properly understand? Thanks, all, for your advice!