Bifold doors fold by allowing one section of the door to slide along an overhead track, while the other section of the door remains fixed in position. To do this, one end of the door has a top pin and a bottom pin, each of which fits into a bracket. If you want to avoid drilling into a tile floor to install the floor bracket, obtain an L-bracket for the bottom. This type of bracket allows you to attach only one side of it to the door jamb, avoiding the need to attach it to the floor.
Cut the door track to the right length to fit the overhead opening in the doorway, using a hacksaw. Attach the track to the door header with screws, using a power drill.
Attach the hardware to the bifold door, including the guide roller and the top and bottom pivot pins. Tap each part into the door with a hammer.
Position the vertical edge of the L-bracket against the door jamb with the bracket's horizontal edge atop the floor.
Hang a plumb bob, which is a metal weight with a pointed tip that is attached to a string, from the center of the overhead track near the side jamb. Position the L-bracket so that it aligns with the plumb bob, which in turn aligns the bracket with the overhead track.
Attach the L-bracket to the side jamb, with the bottom of the L-bracket sitting atop the tile floor. Install screws through the bracket to anchor it to the jamb, using a power drill.
Hold the door in the opening at a slight angle, and push the top pivot pin, on the door's outer edge, into the bracket inside the overhead track. Lift up on the door, and sit the bottom pivot pin into the proper hole or slot inside the L-bracket. Press down on the guide roller to line it up with the overhead track. Release the roller so that it fits up into the track.