Locate the ceiling studs once you picked the ideal spot for your tubular skylight. Drill a hole big enough to push a straightened wire coat hanger through to the attic.
Go up to the attic and find the hanger wire, making sure that the space between the roof joists have no obstructed items in the way.
Shine a flashlight along the coat hanger and between the rafters. Drill a second hole through the roof. Insert another coat hanger through this second hole.
Go up to the roof. Center the exterior flashing of the skylight over the coat hanger on the roof. Trace the internal diameter of the flashing on the roof with a chalk. Use reciprocating saw carefully to cut out the hole.
Screw the skylight flashing in place and install roofing shingles around the flashing to create a seal. Caulk the area where the shingles meet the flashing, let dry.
Install the skylight dome per manufacturer's instructions over the skylight flashing. Clean off the roof area, as needed.
Line rugs on the floor directly under the ceiling where the skylight tube would be installed to make cleanup easier. Mark the outline of the hole on the ceiling and then cut it out with a drywall saw.
Assemble the skylight tube by connecting the tubular sections to match the distance between ceiling and roof. Attach the diffuser, if provided, following the manufacturer's instructions sheet and set the angle according to your lighting/privacy preference. Insert the skylight tube through the ceiling hole and attach it to the roof just under the exterior skylight flashing, using aluminum tape. Wrap the seams of the skylight tubular sections with duct tape for reinforcement.
Screw and tighten the flange to the ceiling (on the attic side) around the skylight tube. Secure the skylight tube section connecting to the ceiling with aluminum tape.