Setting method:
To create a group SMS in Google Messages, you can do the following:
1. Open the Google Messages app.
2. Tap the New Message/Start chat button.
3. Select the contacts you want to send a message to.
4. You'll be prompted to create a new group.
5. Enter a name for the group, or skip this step by tapping Skip in the top-right corner.
6. Type your message in the message window.
7. Your message will be sent to all the selected contacts at once.