how do I edit prefab variables?

I have an enemy script attached to my enemy with a Player var. Then enemy object is also set inside a prefab. I drag the player object into the var on the original object and it turns bold, the prefabs script shows "None" in the transform, I need the player object inside the player var on the prefab. Why is this happening?

If you have it as a prefab, then there should be a button in the inspector called: Apply. It will then use the changed values from your marked game object and apply the changes to your prefab.