Enemy AI will not attack Player

Hi, I'm relatively new to Unity and I'm just now getting comfortable with the UI and all the tools and whatever. Anyway, I'm making a survival-type game and I need my player to be attacked by custom made zombie characters. Now, I know there are a lot of scripts that allow for this to happen, but I'm unsure about the animations. Are 'Idle', 'Walk', and 'Run' pre-made animations in Unity or do I have to make them myself. Or would I have to move the joints of each zombie to create the effect of running???

I have a script from Brackey's called AdvancedAI but it only seems able to turn the zombie so that it is facing the Player, but it doesn't actually make advances towards the Player.