To register for Pag-IBIG online, visit the official Pag-IBIG website and navigate to the online registration section. You'll need to provide personal information, such as your full name, birth date, and valid identification. Make sure you have a valid email address, as you'll receive a confirmation link. After completing the form, submit your application and wait for the confirmation of your registration. For detailed steps and requirements, check the Pag-IBIG Fund's official site or contact their customer service for assistance.