apple watch series 5

How to remove apps from your Apple Watch

1. On the Apple Watch's watch face, press the Digital Crown once to get to your app list. ... 
2. Press lightly and hold on an app icon until it goes dark and begins to wiggle.
3. Swipe around the screen to find the third-party app you wish to delete. ... 
4. Tap the app icon.
5. Tap Delete App.

As a small followup, not all apps can be deleted. Such as Mail, Activity, Clock, etc...