To use the calendar sync with your Apple calendar, you need to create a special "app-specific password" inside of your Apple account.
Here are the steps:
- Log in to your Apple account here
- Make sure you have turned on either two-step verification or two-factor authentication (most people have this "on" by default)
- In the Security section, click "Generate Password" under the app-specific passwords section
- Type "Bookedin" to give a name for your app-specific password, then click "Create"
- Now copy the password, and leave this tab open until you've completed the next step.
- Now open a new browser tab, log in to your Bookedin account
- Go to the "Settings > Calendar Sync" page (top menu)
- Click "Add New Calendar Sync" button
- On the sync setup screen, choose the iCloud option
- Sign in using your AppleID email address, and the app specific password you setup in step 5 above.
- You're done! Now your Apple calendar will sync automatically to your bookedin calendar.