Using a pair of scissors, cut your fabric into the largest squares that you can handle easily.
Determine the point that is roughly the center of the room. Place a ladder below that point and climb up, bringing the fabric and a staple gun with you.
Staple the center of one fabric square to that approximate center point.
Staple the fabric to the ceiling again about 1 foot from the original staple, leaving fabric hanging down between the staples. This swag adds texture and motion to your ceiling while hiding the defects beneath it.
Repeat until the entire square is stapled out to its edges. You can create a very regular effect by placing the staples in a grid, or you can create a more organic look by simply swagging the fabric at random and stapling it to the ceiling.
Repeat steps 4 and 5 with the other squares of fabric until the ceiling is covered.