How Android wear works

To start the Sports Tracker app on your watch, you don't need to do anything as long as you have the Android Wear and Sports Tracker application installed on your phone. You can start, pause and end your workout and follow your workout details in your watch. This means you'll still need to carry your phone with you, but you don't have to take the phone out of your pocket.

It's very simple to start a workout. You can do it directly on the watch (or with the phone if you wish) and also with voice commands. Google provides a few defaults (start running, start cycling and start a workout) which can't be modified at the moment. (Note that if you have multiple fitness apps installed, you need to configure which app is launched with the voice commands from the Android Wear app.)

Starting/pausing/ending a workout is done on the first page of the tracking mode. You can then swipe between pages as in the phone app. Once you end the workout, you can see the summary in just one screen by scrolling down.
If the app is not installed in the Wear OS device then you should go to the Play Store app in the Wear OS and in the first screen (`Home`) scroll down until you see Sports Tracker and tap the arrow to install it.

Once installed just start a workout from the phone.