No synchronization

Hello there, Xiaoxiazhou!

Thanks for reaching out to the Apple Support Communities! That's a great question you have about what settings you need to set up to sync information between your iPhone and iPad. This can be done by following the steps in this article to Set up iCloud on your iPhone, iPad, or iPod touch. iCloud will sync the information across the devices being used with the same Apple ID.

If this is not the path you're needing to go, feel free to circle back with more information about your question.

Have a terrific day!