To sync your Calendars:
Click on the top left Profile icon to go to the Navigation Menu.  Click on Settings. Under Calendars, click on Synced Calendars.  If Owaves does not have access to your calendars, click on "Open Settings App".  This should bring you to Owaves in your iOS settings. Turn on the toggle for Calendars. If you do not see a toggle for Calendars, please refer to the instructions below.  Return back to the Owaves app, to Settings, and to Synced Calendars.  Check the calendars you want to sync and click "Done" on the top right corner.
If you do not see a toggle for Calendars in Owaves in your iOS settings:
Go to your iOS settings. Tap on Screen Times, and then on Content & Privacy Restrictions. Make sure the toggle for Calendars is turned on green. Return to Owaves in your iOS settings and you should be able to see the toggle for Calendars.