This video will show you how to remove the rear tail light (inner) from your Audi A4, S4 or RS4 (B6 and B7).
This is performed on a B7 Avant, but the B7 saloon is similar and so this video can be used as the basis to remove the rear tail light from the saloon also.
Looking for tools? https://www.amazon.co.uk/shop/totaltechnik
Video by TOTAL TECHNIK.