Update watchOS

Check the watchOS version on your Apple Watch, in Settings | General | About. If lower than version 9, update to watchOS 9 for free in the Watch app on your iPhone.

Install apps on Apple Watch

Install watch face complications

Troubleshooting

If the watch app does not install, the following may be useful:

App Permission

Make sure to turn on read and write permissions for Tempori in the Settings App, in Health | Data Access & Devices.