how do i sync my iphone to my ipad

If they are logged in to the same Apple ID, on each device go to Settings/[your name]/iCloud and turn on the switches for the items you want to sync, then leave both devices plugged in and connected to Wi-Fi until the sync appears to have completed.

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In addition to the aforementioned iCloud method, you can also do it this way:

Sync your iPhone, iPad, or iPod using your computer - Apple Support

The slight advantage of using a computer is if your media collection contains items that are not part of iCloud and won't be synced that way.