your watch, you need to charge its battery using the USB charging
clip and either the optional AC adapter or a computer with a USB
port capable of charging external devices.
It takes approximately 2.5 to 3.5 hours to fully charge your
watch, depending on your charging method.
Charge your watch in an environment with a
temperature from 41 to 95 °F (5 to 35 °C).
charge your watch in an environment outside the required
temperature range, you see this screen on your watch: