To install a pocket door, frame in an opening, put up and secure the structure, attach door plates, insert hangers in the track, install the drywall, fix guides at the pocket's mouth, install head jambs and fix the door casings. Paint the door before installing the structure.
Frame the width and top of the door according to the manufacturer's instructions. Add 1 inch to the width. Plumb the rough opening, and level the header.
Cut the header and track assembly with a hacksaw. Use brackets and fasteners to install the header. Put up two metal supports to strengthen the pocket. Fix the jamb stiffeners, which are the first set, ensure they are upright, and secure them to the floor. Install the other set of stiffeners, called the side-split jambs, at the center of the pocket framing, and attach the door bumper to the stud on the backside of the pocket.
Once the hangers are fixed, hang and adjust the door with nuts in respect to the height and plumb of the door. Fix the drywall on the frame with construction adhesive. For smooth sliding, ensure that the door guides are flexible. To reinforce the casing, nail it, glue the miters, and apply the construction adhesive at its back part.