To make an object track your face, you have to make it the child of a Face Tracker.
To do this:
Note: To insert objects as children of other objects directly, you can also right-click on the parent in the Scene tab, select Insert and then select the object you want to insert from the menu.
You can add more than one face tracker to a scene, but you can’t add more than one to a face. You would add more than one face tracker if you wanted to track multiple faces within a scene.
To enable multiple faces: