I see that you have used the People Management starter file to create your solution. In the original Employee table that you are now using as your Customer table, there was a field called Employee ID. This was defined as an auto-entered serial number. It is this (rather than the full name) that should be used as the customer identifier in a relationship to their appointments.
Therefore, your Appointment table should have an 'employer ID' field (or whatever you call it now), to act as a foreign key - the link back to the customer.
The relationship you create between the customer and appointment tables will be:
Customer::EmployeeID = Appointment::EmployeeID
This will enable you to create a portal and display appointments for each customer.
If in doubt, create another copy of the People Management file and have a look at the relationship between Employee and Goals.