Press the button of your BPM once to turn it on. Note that if you press the button during a measurement, it will stop the measurement.
Press and hold the button of your BPM for three seconds to turn it off.
https://support.withings.com/hc/en-us/sections/6215855075857-Wireless-BPM
https://support.withings.com/hc/en-us/sections/200334438-Tutorials
