How do you keep your watch face on. I have to press the side button to see the time.

If as your tag line suggests, you have Apple Watch 8, do you have Always On turned on in Settings > Display & Brightness in the Watch App on your iPhone or in the Settings app on your watch?

If you do and Always On isn't working, from the bottom of your watch screen swipe up to open Control Center. See if the icon with two masks (Theater Mode) is highlighted and if it is, tap it to turn it off. If that isn't the issue, on your watch, open the Settings > and swipe up till you see Battery and make sure Low Power Mode isn't turned on. If it is, turn it off.