Have your closet door operational in 15 minutes. Here's how:
Build the Frame
Measure the door opening and cut the fram to length. Make sure it's square, and nail it together.
Set and Attach the Frame
Set the frame in the opening. Use a level to ensure it's plumb. Insert shims where needed to provide a nailing surface. Do this to all sides except the bottom, then nail the or screw the frame in place.
Trim the Door
Measure the door, adding in the track dimension. Measure and trim the door accordingly. Trim with a circular saw or score with a utility knife.
Attach Top Track
Use the manufacturer hardware and instructions to attach the top track to the frame