You will need to remove the undertray / open the sump access cover
Undo the fixings - use a screwdriver
Do not forget to have a suitably sized receiving tray in place
With an oil catchment tray in position, use a 19mm spanner or socket to carefully remove the sump plug. Fully drain the oil.
When the sump has emptied, wipe clean the sump plug area with a paper towel
Replace (new) sump plug and washer. Do not over tighten - Replace undertray
Find a Haynes product for your Audi:
Search by registration mark
Search by make & model