Follow the below mentioned steps to Schedule SMS in DO SMS Panel:
Login into your DO SMS Panel
Click on the "Send SMS" option available in the Left Side Menu
Select the SMS Route as per the requirement
If the default Sender ID is not set then type the Sender ID from which the SMS is to be sent
Under the "To:" field, type/Select the contact(s) to which the SMS is to be sent
Under the "Message" box, type the message to be sent
Under the "Campaign name" field, type/Select the Campaign Name
Click on the "Schedule SMS" option available on the right side of "Send SMS Now" button
Under the "Date, Hour, Minutes fields", select the "Date, Hour and Minutes", on which the SMS is to be Scheduled and press the "Schedule" button to schedule the SMS
See our article on the process of generating Scheduled SMS List: Click Here
See our article on TRAI Rules for Sending SMS : Click Here