Locate the area in the soffit where the bathroom fan will be vented. Mark and cut a hole for the vent cover according to the manufacturer's instructions. A hole saw or jigsaw may be necessary.
Secure the correct pieces of vent pipe needed to attach to the boot where the pipe meets it, but do not attach the pipe to the boot yet. Slip this pipe through the hole that you cut and into the attic.
Locate the bathroom fan in the attic and secure the first piece of vent pipe to it. Continue to connect the pieces, making certain that they travel in the direction of the vent pipe you slipped through the soffit.
Cut a piece of plumber's strap with the tin cutters that will fit over the top of the vent pipe and to the ceiling joists. Secure it with the drywall screws.
Secure the pipe coming from the bathroom fan to the pipe inserted through the soffit. Next, return to the soffit outside, connect the vent pipe to the boot and slip it in place. Secure the vent cover to the boot with a screwdriver.