Mobile phone railway 12306 where are the common contacts added?

1 Whether it's an iphone or an Android phone, we click on "Railway 12306" and find "my 12306" as shown below, then click on my name. (pictured below)

2 below there will be a "common contact", and then we click on Open click "Add". (pictured below)

3 finally enter the information of the common contact person click "Finish" on it. (pictured below)

PS: Common contact is required to log in before you can view, we can use the same as the PC account on the phone login oh, because they are interlinked.