Plug the battery pack into the pocket at the top of the sock, switch the battery pack on, then hold the button on the sock for 3 seconds until it glows red, and your sock warms up in seconds. Press again to change the setting, shown by the light: green Eco up to 40°C (5-6h), blue Medium up to 50°C (4-5h), red Power up to 60°C (3-4h). Hold the button for 3 seconds again to switch off.