This lever can be found on the Right side of the steering wheel.
The switch on the left of the lever should always be left on AUTO as shown below. This means that the wipers will automatically engage once it starts drizzling/raining. The speed as well will be automatically adjusted according to how heavy the rain pours.
To activate the wiper at the back, turn the switch on the right side of the lever up once for low speed, and twice for high speed. Do remember to switch this off once you are done.
To spray the water jet onto the windscreen, pull the same lever towards you. 💦