Yeah, for an enemy you can find a model online, use a basic cube or cylinder, or make a model in Blender. Using Blender is pretty complicated so I would use some other model or a basic shape while you get started, you can always make one later. Then for enemy navigation you can use the built-in navigation system.

However, if this is your first time making a game, I would work on the first person controls before tackling navigation or modeling. For your first game you pretty much need to follow a tutorial to learn how to use Godot, so I'd find a tutorial like this one on how to make a first-person game. It could also be helpful to follow a basic tutorial like this one just to learn how Godot works. Learning how to make games is pretty difficult so don't worry if it takes you a while to get things working, especially if you don't have any programming experience.