You can view, create, complete, and edit reminders from the Reminders app right in Calendar.
You can show scheduled reminders you added to the Reminders app at the top of the screen.
Tap Reminder, then enter a title.
To choose a date for the reminder, tap Date.
Optionally, turn on Time and choose a specific time for the reminder.
You can also add other information—like images, notes, or a priority level to a reminder. See Edit and organize a list in Reminders on iPhone