Tracking steps on series 7

If you go to the Activity app (the icon is the three rings) and swipe down, you'll see your steps.

If you want to see the steps on the main watch face, you'll need to get an app such as StepsApp that will allow you to put a steps complication on the face.

Change the watch face on your Apple Watch - Apple Support

The watch keeps a running total of steps you do in the course of the day;