Using Siri: Just press the digital crown and say “In Things, remind me at 5 PM to contact Sarah about our trip”. This adds the to-do to Things on your watch, with a reminder set, and syncs it to your other devices.
Inside the app: You can also tap the + button inside of Things to dictate or scribble your to-do. If you want to work on it right away, quickly tap the animation to move it from the Inbox to your Today list.
Focus on a project: If you know you’ll mostly be working on a given project throughout the day, simply add that project to Today on your Mac, iPad, or iPhone and it will show up on your Apple Watch.
Notifications: To be reminded about your scheduled to-dos, make sure Notifications are enabled in the iOS system settings on your iPhone.
Append notes: Not only can you view your to-dos’ notes, you append new ones on the go – via dictation or scribble.