With StepsApp you can start and Outdoor or Indoor Walk or Run and track steps, heart rate and active time.

You can start a workout on Apple Watch by following these steps:

• Choose your Workout by swiping left on the watch app (e.g. Indoor Walk)
• Tap on “Start” and start walking
• Finish the Workout by swiping right and tap on “End”
• Analyse your data and scroll down, then tap on “Done”

Here's a detailed video about Workouts on Apple Watch: https://youtu.be/MyKSPXmXVdU