Client Contacts do not appear on the calendar as they are designed to be used for things that have occurred in the past.  

You have options to create an Appointment, a Client Contact, or a To Do item from within an event under Contact Manager or you can create them by going to Main Menu -> Add Appointments.  

Here is a brief explanation of each:

Appointments: You create appointments for things you would like to have happen in the future, such as setting up a meeting, scheduling a phone call, etc.  These appointments can be set up for Clients, Venues, Employees, Vendors, and Other Contacts.  Appointments show on your calendar on the dates they are scheduled on. They will also show on the side panel when that date is chosen.

Client Contacts:  These do not appear on the calendar.  Client Contacts are entries of contacts you have made with Clients in the past.  For example, if you had a phone call with the client at 3:00pm on November 4th you would add that Client Contact to your system by going to Main Menu -> Add Appointment -> choose Client Contact, then enter the details.  Client Contact information is tied to the Client's Contact Manager information.  If you need to have this information appear on your calendar, then you will need to create it as an Appointment.

To Do: To Do items are simple reminders for you or your staff.  For example if you need one of your employees to re-order batteries for equipment, you would create a To Do item for that staff member.  To Do items only appear on the left hand menu and the contact manager tab of the employee it was assigned to.   A To Do item stays on the dashboard until it is marked as completed.