On your Mac, choose Apple menu Set up iCloud for Reminders on all your devices.
Use this method to add a reminder account from other providers that offer reminders, such as Yahoo.
Note: Some features in Reminders aren’t available when using accounts other than iCloud.
On your Mac, choose Apple menu in the sidebar. (You may need to scroll down.)
In the list of accounts on the right, click the account you want to stop using.
Turn off Reminders.
To use the account again with Reminders, turn on Reminders. The account’s reminder lists and reminders reappear.
You can view, add, and modify reminders in the Reminders app on all your Apple devices when you’re signed in to the same Apple Account. Changes you make show up everywhere, so you always have your most current reminders at hand. Reminder notifications also appear on your Mac and other devices that use the same account.
If you Apple Support article: If your iCloud Contacts, Calendars, or Reminders won’t sync