From Xojo Documentation
The AddressBook class gives you access to the AddressBook. You can also access the AddressBook using System.AddressBook:
To get the contacts in the Address Book, use the Contacts property:
Each contact has properties for the various fields, such as FirstName, LastName, etc. To add a contact, create it and then add it using the Add method:
contact.FirstName = "Bob"
contact.LastName = "Roberts"
AddressBookAddress is used to get address information for a contact. AddressBookData is used to get information such as email addresses, phone or fax numbers. AddressBookGroup gives you information about all the groups in the address book. Use the AddressBook.Groups property to get an array of groups.