1. Install on iPhone & Watch
Step by step get it working on your iPhone and Apple Watch.Pls note the watch app in addition requires ... Register watch with iPhone 'Register Watch'
2. Register watch with iPhone
A 3 step process to add the watch app to the iPhone's Alperton app licence
3. Settings for Watch
Simple settings, however, more involved initially when to link to phone & restore license. However, it has specialised three step procedure for peace of mind,Task 2 above
4. Settings for iPhone
Really self explanatory.
5. Making use of barometer data stream
This is a proactive thing. Trial & error.