Put the two metal side rails of the frame on the floor, placing the ends with the headboard attachments at the head of your bed.
Attach the metal crossbars at the head of the bed, the middle of the bed and the foot of the bed with the bolts, nuts and washers that come with the frame. These crossbars are required to support the weight of the waterbed.
Insert the feet into the legs that are on the crossbars. Each crossbar will have three legs--one on each of the side rails and one in the middle of the bed.