Great question! 3 easy steps.
1 - Hang it in any sunny window. It takes 8-10 hrs of direct sunlight to fully charge the built in battery. A suction cup comes with the product for hanging.
2 - Plug your phone or USB device into the included USB port.
3- Charge all your favorite small USB devices from the charger's internal battery. A full battery can charge iPhones (2x), Android phones (1 - 1.5x), Tablets (0.5x), Air Pods (3x), Portable Speaker (1x), Donuts (1000x).
The sun charges up the Window Solar Charger's internal battery all day so when you get home from work, school, outerspace, or wherever it's ready to go day or night.