I have done this for my child. According to my memory, the process involves the legal guardian bringing the device or a photo of the device (as required by online verification), the minor's ID card, the legal guardian's ID card, household registration book or birth certificate (to prove the relationship between the legal guardian and the minor), and going to the association on weekdays. The minor does not need to go; if there are any concerns, you can call the association to inquire.