Identify the two front strap slots on your strapless bra. They should be located on the outer edges of each cup. Some bras have two slots in the front, one closer to your breast and the other closer to your armpit. If your first strap installment is uncomfortable, switch the placement of the bra strap to a different slot.
Attach one side of the detachable strap to one of the slots. Slide the hook into the slot until it slides no farther.
Hook the opposite end of the strap to the other slot.
Adjust the strap to optimum comfort. Don the bra, sliding your head beneath the strap so it crosses behind your neck. Slide the strap adjuster to loosen or tighten the strap, depending on how snug or wiggly you want it. If you can't get the strap over your head, don't stretch it; it might snap. Loosen the adjuster and give it another shot.