You just need to download the Hand Wash app to get started.

A new app called the Hand Wash app works with your Galaxy Watch to remind you to wash your hands. The app will send a notification to your wrist every 2 hours to let you know its time to go clean your hands. You can also manually set your own personalised interval. The app also adds a handy timer to your Galaxy Watch that you can activate when washing your hands so you can make sure that you do a proper job of keeping your hands clean in a time where hygiene is everything.