Check that you have a complete set of parts: It is important that you consult the user manual and that you have all the necessary parts to install it, such as: backrest, cushion, body structure, seat, wheel, star base, air piston, screw and washer.Installation of the seat mechanism: turn the seat over and position the mechanism according to the instructions, so that the holes in the mechanism match the holes in the seat and the screws.Attach the wheels to the star base - You can now attach the wheels to the base by inserting them into the holes provided, each wheel should be pushed in until you hear a click.Connect the base to the air piston: As the part that connects the base to the seat, the piston must be placed in the hole in the center of the base and then the protective cap must be put on.Seat mounting: You can now mount the seat to the gas piston.Attach the backrest to the chair: Finally, fit the backrest by matching the holes with the metal parts of the chair and then tighten. Then put the trim on the metal that joins the seat to the back, secure it with screws and finally install the cushion.