Memory too full to add update. How do I clear space?

Hello, I am using Watch series 3 and iPhone 7. You will likely find what I have, that you need to unpair your watch from your phone and re-pair it as a new device. Then there will be enough space to conduct the upgrade. When adding the watch back you can restore a backup.

This doc should cover all the details: Update your Apple Watch - Apple Support

And, this refers specifically to the issue of not having sufficient space: If you don’t have enough space to update your Apple Watch – Apple Support

Press the Digital Crown on your Apple Watch to bring up the App View.

If you're using List View, swipe left across the app you want to remove, then tap the red trash button. If you're using Grid View, tap and hold to activate jiggle mode, then tap the X in the top-left corner of the app you want to remove.

Tap Delete App to confirm.

Not all apps are available to delete.