2 Questions About Loading Animations?

I've seen games that have some Roblox animations but with some experimenting I found out the animation needs to be uploaded to your account for it to work. How would I put in a Roblox animation?

Animations on my NPC don't seem to work. It works on another NPC with the rig builder with the exact same script but not on an NPC I got with a character loader. I deleted the head and 2 accessories aren't welded to it or anything but I doubt that's the problem. Could there be any reasons/factors?