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.
Open the tailgate.
Take the screwdriver out of the Audi Q5 tool kit Link.
Use the flat-blade side of the reversible screwdriver insert and carefully lever off the appropriate covers Fig. 1.
Take the bulb holder for the defective bulb (turn signal -A- or inner/outer brake light -B- Fig. 2) out of the light unit Link.
Change the bulb Link.
Re-install all parts in the reverse sequence and check that the bulb is working.