Completely remove older headlight including both chrome rings, so that the black headlight casing is visible (photo 1).
You will need two NEW rings which are designed for 7" headlight. Attach inner ring to black headlight nacelle by two screws at 4 and 8 o'clock positions.
Headlamp bulb is secured to outer ring by W-shaped-retaining-clips. NB - These clips can spring back and fly very fast and hit face. So WEAR EYE GLASSES. To put them on, put one end of W-retaining-clip into groove of outer ring and hold/push at its center with left thumb while attaching other end into groove of outer ring with a plier. Or Place towel on top while working with pliers.
Once headlamp is secured in outer ring, its bottom tab goes into a slot of inner ring and top fixing plate positions are shown in photos 2 to 4.
The 7" headlight is essentially non-adjustable - fixed. However, if the holes in rings are elongated, that allows some movement for slight adjustment.
PS - I am making a video for this and will post it on youtube hopefully this week.