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