Mount the headboard brackets to the bed rails by aligning the bolt holes. Place a bolt through both pieces, and secure it with a nut. Repeat on the other side.
Mount the footboard brackets to the other end of the bed rails. Remove any end caps, if present. Slide a bolt through the bolt holes in both the bracket and the frame. Twist a nut onto the bolt until the bracket is securely on.
Place the headboard next to the headboard brackets. Align the bracket bolt holes with the headboard post holes. Insert a bolt and secure it in place with a nut. Repeat with the other end of the headboard.
Attach the footboard the same way as the headboard, by inserting bolts into the footboard bracket bolt holes, all the way through the footboard. Secure the bolts with nuts.