Scripting an animation for an NPC?

I've got my enemy AI script set up and it works great. When I get closer to my enemy, the enemy gets angry, chases and attacks me. The next step is to get the walking/running animation for my NPC. I understand how you would animate the player walking,have something like Input.GetButtonDown()and then have it triggered to whatever key you are using to walk forward. I'm a bit confused on how to have it on the NPC. maybe something like if the position changes? Thank you!