I think this is a game design question first, playmaker question later.
There are many ways to create an Enemy AI, maybe you're just checking distance and activate the chase when the player is close enough, maybe its that but also when the player is within the right field of view. You could also use raycasts, but on some games it could be a tile logic or just showing up on the screen.
If you want to just do the distance, you can use the action Get Distance, and feed that value into a Float Compare. The chase could either be with a simple Move Towards or if you're using Unity's pathfinding you could se the Enemy Agent's target as the Player object.