My watch is not showing steps when I do my walk or run activity
You did not tell what watch you use, but on many models, when you want to have a look at the steps during an activity, you just need to press the Escape button (right bottom in my case), to get to the main screen, where you then scroll down to the Steps and/or Floors screen, and then press the Escape button again to get back to the Activity screen.
and no steps or stairs are displayed in the app on my phone
You need to synchronise the watch with th phone first. If it does not happen automatically, then you'd need to lookup sync troubleshooting instructions for your conditions.
