Use a power drill to drill a screw into the end of each chair leg. This screw will attach the leg to the chair seat.
Drill four holes in each corner of the underside of the chair seat. The holes should be slightly smaller than the screws that are on the ends of the chair legs.
Use a hammer to secure a T-nut to each of the four corners of the chair seat.
Screw each chair leg into a T-nut on each seat corner, tight enough so the leg is flush against the seat bottom.