In Planable, when you create a post (find out how here) it can be saved as a Draft with or without a date and time.

After you save it as a draft, you can see it if you go to the Calendar view, make sure that you have Show saved turned on, and in the saved posts lists you can see all your draft posts and you can schedule them by drag and drop them to the specific day in the calendar.

Schedule your draft posts 👇