When you hook up a third party calendar integration (e.g. Google Cal, Office 360), you may need to specify which calendar categories you want to include. This will only be the case if you have existing categories in your third party calendar that do not pertain to the member's booking availability.
Appointlet will automatically detect your existing calendar categories when you hook up the Calendar account. All you need to do is specify the calendars that you want to include.
To set this up, go to Members & Availability, select the member you want to edit, and open the Calendar section. If you have not hooked up your calendar yet, see this tutorial. If and when the calendar is hooked up, simply edit the Availability Calendars field by checking the boxes next to the calendar categories that you want to include.