You will need to remove the undertray
Undo the fixings - use a 10mm socket
Don't forget to place a suitably sized receiving tray in place!
With a oil catchment tray in position, Using a 8mm SQ socket, carefully remove the sump plug and fully drain the oil.
When the sump has emptied, wipe clean the sump plug area with a paper towel and refit the sump plug and washer
Replace (new) sump plug and washer. Do not over tighten