Head over to your dashboard and click on Calendar then + add new > text.
The title of the custom test is only visible to you and will not be seen by the recipients.
On this screen, you should type your message in the body section.
Once your message is complete scroll down to the Approve to Send section and choose which option is best for you.
SEND NOW will send in 10 minutes.
Then select the group you want to communicate with and hit SAVE.