This one is very similar to yours.
Slip the one leg of the (longer) lower metal piece through the strap loop at the end of the D ring side of the helmet strap, then slide the plastic doo hickey on to the metal piece.
The smaller (upper) metal piece goes on the other side of the helmet strap.
It is highly likely that you can (and probably should) keep your factory D rings in place.
The photo shows the three pieces in correct formation for how they will fit together.
