How do i make a Custom character in studio with animations?

Me and my friend are working on a game where you play as a cat. so i need to make a custom Starter Character, i have been using this video:

https://www.youtube.com/watch?v=c5pLIx3PsN8

But after binding the joints and doing everything the video says when i open the animation editor and select the "HumanoidRootPart" and try to rotate a body part, it wont rotate.

if anyone knows how to solve my problem or even if you know another way of creating a custom starter character with animations please tell me in the comments.

thanks.