Unscrew and remove the screws holding the awning tube to the awning rail. Unscrew and remove the mounting brackets located on each end of the awning rail.
Unscrew and remove the patio feet from the mounting brackets. If your awning has an adjustable arm, unscrew and detach the adjustable arm from the awning tube.
Grip the top casting on each side of the awning tube with a grip wrench. Hold the casting steady with the grip wrench. Unscrew the hex screws holding the casting in place with a hex wrench.
Pull casting free of the awning tube. Remove the cotter pin and let the the torsion spring unwind. Keep a tight hold on the casting with the grip wrench until the torsion spring unwinds completely.
Lift the awning tube away from the awning rail. Roll out the awning fabric on a flat surface. Slide the fabric off the awning tube. Discard the old tube and casting.
Spray the new awning tube with silicone lubricant. Slide one end of the fabric into the fabric receptacle on the awning tube.
Set the new awning tube in place on the awning rail bar. Re-attach the mounting brackets. Insert screws into the awning tube's receptacles. Each screw should pass through the awning tube and into the awning rail. Tighten the screws with a screwdriver.
Roll out the loose end of the fabric from the awning tube. Slide the loose end of the fabric over the awning rail. If your awning has an adjustable arm, re-attach the adjustable arm to the awning tube.