Kensington H3000 Bluetooth Over-Ear Headset - Manual (Page 11)

To charge the headset, connect the USB-C charging cable to the headset's charging port. For USB-C connections, plug the USB-C end into any available USB-C port on your device.
For USB-A connections, connect the USB-A adapter to the USB-C receiver, then plug the USB-A adapter into any available USB-A port.
15 minutes of charging time will provide 8 hours of headset use. 90 minutes of charging time will fully charge your headset battery to 100%.