Here, you will need to link the the ABAddressBook framework first though. To do that, you will need to (in XCode) goto Project > Edit active target "TargetNameHere.app". Press the add button on the lower left hand corner, and find AddressBook.framework (is usually the first there). Click add.
import <AddressBook/AddressBook.h>
// CODE BETWEEN START OF FILE AND ADDING ADRESS BOOK ENTRY.
ABAddressBookRef ab = ABGetSharedAddressBook();
// To add a new ab entry with telephone number
ABRecordRef newPerson = ABPersonCreate();
ABRecordSetValue(newPerson, kABPersonFirstNameProperty, @"Bob", nil);
ABRecordSetValue(newPerson, kABPersonLastNameProperty, @"Jones", nil);
ABRecordSetValue(newPerson, kABPersonPhoneProperty, resultText.text, nil);
ABAddressBookAddRecord(ab, newPerson, nil);
ABAddressBookSave(ab);
For the sake of space, I didn't check for NULL, or pass in error pointers and check for errors, but you should do this.
This code should go in a .m file of the class that wants to add an Address Book entry; most likely in the function that currently has access to resultText.text
.