If you'd prefer to send your message at a later time, use the Schedule delivery option on the Send message button's dropdown list.
A window will pop up with options for your scheduled delivery.
Enter a Name for this schedule and (optionally) a description. Then select the date and time you'd like your message to be processed and delivered.
You can view your scheduled messages on the Scheduler page.
Please note that changes to message templates and scenarios will not change the content of a scheduled message.