how do i change the apple id to my phone

See Use your mobile phone number as your Apple ID https://support.apple.com/en-us/HT207944#change-appleid See the heading Change your Apple ID to a different mobile phone number.

See Use a passcode with your iPhone, iPad, or iPod touch See the heading Change your passcode or passcode settings https://support.apple.com/en-us/HT204060#adjust

You want to use a different Apple ID on your phone? Or you want to change the email address on your existing Apple ID?

Use a different Apple ID.

When changing to the new ID, there may be some data loss, but you can minimize it. If syncing photos with iCloud, ensure Optimization is turned off in Settings/Your Name/iCloud/Photos and/or in Photos/Preferences/iCloud. Then make sure full resolution photos are on the device/computer. When signing out of iCloud, if asked whether you want to retain data, choose yes. Messages conversations will be lost if they are addressed to the ID. See the article below for other places that the old ID should be removed. See Winston Churchill's response in the below discussion. Also set up Family Sharing to keep access to your apps/purchases. 

 How to switch Apple IDs on your iPhone or iPad.      

How to transfer all files from one iCloud account to another.       

What to do after you change your Apple ID or password - Apple Support.      

Family Sharing.         

Family Sharing - Set up.        

Change the email address on your existing Apple ID.

Note the restrictions in the article.

Apple ID Name Change.        

 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.