Changing Apple ID on iPad to match Apple ID on iPhone
What part of the iPad do you want to add a new Apple ID to? There are several different places to enter an Apple ID.

Messages

Settings > Messages > Receive at:



App Store

Settings > Store > Apple ID:



Alternatively, you can go to the App Store, click on "Top Charts" at the bottom. Scroll to the bottom and you can sign out and enter a new Apple ID.

 


iCloud

Go to Settings > iCloud > Account: