How to get trigger input on an Xbox controller (Mac)

I am trying to make it so that when I press the right trigger on my controller the laser prefab instantiates. I'm am trying to use unity's input manager but I cannot get it to work. I would like it so that I could do something like this:

if (Input.GetButtonDown("Fire1")) { Instantiate(laserPrefab, transform.position, Quaternion.identity); }

Any help would be appreciated.