Never mind, I got it. First, I just have to add AddressBook.framework into my Linked Frameworks. Then, this is the code required:
#import <AddressBook/AddressBook.h>
NSString *theEmailAddressWeWantToObtain = @"";
ABPerson *aPerson = [[ABAddressBook sharedAddressBook] me];
ABMultiValue *emails = [aPerson valueForProperty:kABEmailProperty];
if([emails count] > 0)
theEmailAddressWeWantToObtain = [emails valueAtIndex:0];