Two-person assembly: Lean headboard against the wall near desired placement. Lift up on the top of one siderail/wing and slide the shoulder bolt (which is on the inside top wing) into the keyhole bracket at the top of the headboard. With one person holding the side rail up against the bracket at the bottom of the headboard, hand-start bolts (to avoid cross-threading) and tighten. Repeat for the second rail.
One-person assembly: Start with the headboard on its back and invert the rail to install. Ensure all bolts are tight before tipping down. Repeat for second rail.
NOTE: If you experience difficulty aligning bolts with t-nuts, loosen the headboard bolts to help with alignment. Tighten all bolts.