Install the phone app.
To use the watch with a phone, first tap one of the links below and install the “GBA-400+” app on the phone.
iOS (iPhone) Users
https://itunes.apple.com/app/id1483704854?mt=8
AndroidTM (GALAXY, etc.) Users
https://play.google.com/store/apps/details?id=com.casio.gba400plus
