Open the hood of the car.
Locate the windshield washer fluid reservoir. It is typically a translucent plastic container with a blue or green cap.
Unscrew the cap of the reservoir.
Pour windshield washer fluid into the reservoir until it reaches the "Full" mark.
Replace the cap of the reservoir.
Close the hood of the car.
For your reference, here is a diagram showing the location of the windshield washer fluid reservoir in a Mercedes E320:
[Image of a Mercedes E320 engine compartment with the windshield washer fluid reservoir highlighted]
The windshield washer fluid reservoir is located on the driver's side of the engine compartment, near the firewall.
