"To set a reminder" means to create a notification or an alarm that will help you remember something important like an appointment, task, or event. Full definition
You can also set reminders for when certain bills need to be paid, etc.. (stillbeingmolly.com)
So set a reminder on your phone or calendar because if you go over by a few hours, you're not getting your money back. (singleroots.com)
Try to stay as close to your regular pumping schedule as possible by setting reminders in your phone and adding it to your calendar. (sarahwellsbags.com)