What kind of information do you need to input and how interactive do you want it to be? If it is very basic, you can create new table for appointments, and create a calendar report within that table. Your fields could be something along the lines of:
1. Appointment with
When you have added your appointments, create a new calendar report and filter it as necessary. When customizing the calendar report you can show as much or as little information as you want. Hope this helps!