How do I change my email address in my Iphone?

 Do you want to change your Apple ID email address on your current Apple ID so you retain access to your data and prior purchases? If not that, what email address do you want to change? Note the restrictions in the article.

Apple ID Name Change.  * 

Make sure you turn off Find My Phone before signing out of the old ID. Once signed out and Find My Phone is off, then sign in with the new ID, then turn Find My Phone back on.

 What to do after you change your Apple ID or password - Apple Support  *  I suggest doing this before you change your Apple ID or password.