Prefab with a fixed position

I have an object (target) in my scene, which is placed at origin. My bullet prefab is supposed to look at it. I`m creating public Transform in my bullet prefab and then try to drag and drop my target in there. It can`t be dragged. Then I have to create a prefab for target as well.

How do I set its position to origin IN the prefab properties? Many thanks in advance!