To schedule push notification you need to first login with your registered account.
You will be then be directed to the dashboard.
Then go to Notifications > New Notification.
Enter the required details in the given field and make a notification.
Once you’ve completed the above step scroll down and you will find scheduling options. You can choose any of the options, but if you want to send a notification at a particular date and time you can choose Later at and then set date and time.