Link a Contact with a Campaign

I have had a play with the Zoho CRM API and I am not sure how to accomplish what I want to do. I have a Zoho CRM setup where Contacts are mapped to Students and Campaigns are mapped to Classes. When a user registers for a Class in a Wordpress registration system I would like the following to happen.

1) if the Student (Contact) is not in the CRM then create the Student using the API. ( This should be easy )

2) Link the Student with the Class ( Campaign ).

So if the Student already exists a new one should not be created. And if a Student has already attended another Class then again a new Student should not be created.

So in other words I would like to either create a new Student and link the record to an existing Class or if the Student exists then just link/associate the record to an existing class.

Is this possible? If so what methods do I need to use and how.

Thanks for any help.

Pete