Set up as shown, without the lens in place. Secure the laser to the jack with rubber bands.
With the laser beam going through the center of the interferometer double lens plates (near the middle of interferometer), adjust the 2 screws on the plates. Work with them until the beam aligns with no “fish tail” in any direction.
Put the lens in place and you should see Newton’s Rings. Adjust the large front knob to expand or contract the rings.