The sump plug is located on the base of the engine; it is accessed underneath the car. Note - although you can empty the sump without removing the undertray, the undertray will have to be removed to access the oil filter cartridge
Don't forget to place a suitably sized receiving tray beneath
Using a 19mm spanner or 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. Do not over tighten