Messages from your watch are sent using the same phone number as your companion smartphone.
This watch doesn't have the ability to send/receive iMessages. If you're using an Apple® iPhone® with this watch, disable iMessage to receive all text messages as SMS or MMS on your watch.
From the Home screen, press the Power button to display the menu.
The Power button is located on the right edge.
Tap Message+ .
Tap the New Message icon .
Tap Enter Number or select a contact from the Recent Contacts list.
If entering manually, enter the 10-digit number then tap the right arrow icon (at the bottom) to continue.
Tap Voice to Text or select a pre-formatted response (e.g., Ok, Coming Soon, In a Meeting, etc.).
If using Voice to Text, speak your message from the Speak now screen. The message is sent automatically after you stop speaking.