Your ZeSport has been calibrated in the factory (by default).
To calibrate the altimeter automatically, please activate the GPS mode on the watch.
Then, go to the Settings menu (nut icon) of the device, select Sensor Calibration > Altimeter > With GPS.
You need to go outside so the device can locate your position. After a few seconds, it will detect the altitude.
For a manual calibration, please go to the Settings menu (nut icon) of the device, select Sensor calibration > Altimeter > Manual.
Calibrate the altimeter manually if you know the altitude and click on OK.
Barometer / Temperature
The instrument has sensors to determine automatically the atmospheric pressure and temperature.
If you want to set them manually, go to the Settings menu (nut icon) of the device, select Sensor calibration > Pressure or Temperature.
Set the air pressure and temperature manually, click on OK to confirm.