used here:
straps and rings
monarch - ground pose 01
monarch - ground pose 02
load in the standard g3f character.
in the top menu go to "3d garment" -> "attach all pins to avatar"
load in your character as a morph target.
when simulation is done detach all pins, and simulate again to let the garment settle
careful with the little buckles on the lower straps, if they are not in place, stop the simulation and move the top and lower parts of the strap around to get the buckles in place again