- Open the Withings App.
- Tap the Profile icon.
- Scroll to the bottom of the Profile screen to the Family section and tap on your avatar.
- Tap Email.
- Enter the new email address.
- Tap Save.
https://support.withings.com/hc/ja/sections/6216033813649-Withings-App-Android
https://support.withings.com/hc/ja/sections/200501778-Tutorials