Set up a stepladder in the area receiving the recessed light. Mark the distance required for the light on two consecutive metal studs with a dark-colored permanent marker.
Hold the end of a tape measure against one stud face aiming into the cavity. Stretch the tape across the cavity to the other inside stud face. Note the measurement.
Slide the adjustable arms of a stud-mounted light housing to the inside dimension of the stud cavity plus 1 1/2 inches. Hold the housing between the metal studs with the flanges attached to the end of the mounting arms sitting flat on the bottom of each stud.
Set the clutch on a screw gun to a middle number – between eight and 11. Run one No. 6 pan head screw through each flange hole – generally two per flange – with a screw gun equipped with a #3 Phillips adapter.
Slide the center housing left and right until it sits in the required position. Tighten each mounting arm screw, turning clockwise with a Phillips screwdriver until tight.