Flip the cushions over so that you can see the exposed framework underneath.
Insert a frame connector into both of the frame openings on one side of one of the cushions. Slide the connectors so you can see the holes in one end of the connector line up with the holes in the frame. Secure the connectors using the short hex screws that came with the futon. If your model of futon only has one large piece, skip to Step 4.
Place the other cushion against the edge of the first, so that the exposed half of the frame connectors is inserted into the frame of the second cushion. Secure the connectors to the second cushion in the same manner as you did the first. No you will have one large, connected cushion.
Attach the front legs, or the front leg bar, to the front of the frame or cushion. Look for two small screw holes in each corner of the cushion or frame. Install the legs or the leg bar with hex screws using these holes. If you are installing a leg bar, you will have to make an additional connection in the middle of the frame, between the two corners.
Connect the two rear legs in the same manner as you did the front legs. These will connect with screws going through a hole or holes on the back of the frame. Some models may require you to stand the unit upright to drive the screws down into the legs.
Turn the futon upright, if it is not upright already. Find the two slots on the back of the futon, and pull out the integrated legs, just to make sure they are working. Keep these extended if you are going to use the futon as a bed, or put them back into the slot in the cushion if you are going to keep the back of the futon upright.