The description for changing the bulb refers to the left rear light unit; in principle the same procedure applies to the right rear light unit.
Check which of the bulbs is defective.
Take the screwdriver out of the Audi Q5 tool kit Link.
Lever off the cover cap.
Slacken off the screw Fig. 1.
Carefully pull the light unit out of the bumper.
Remove the bulb holder for the defective bulb from the light unit Link.
To change the bulb for the reversing light Fig. 2, carefully pull the old bulb out of the bulb holder and then fit the new bulb.
Re-install all parts in the reverse sequence and check that the bulb is working.