how to add an Apple ID to a lock iphone to have access to previous Apple ID

To have access to the old ID you need to have the sign-in information for the account or you need to use account recovery.

You also talk about a locked phone. Refer to this support article for various methods that you can use to resolve this. --> If you see a iPhone, iPad, or Apple Vision Pro unavailable message or Security Lockout screen - Apple Support Which one you can use depends upon your equipment configuration. If you can use the iOS15.2+ method you may not need a computer.

How to reset your device if you are running iOS 15.2 or later:

Advance step: If you're using an eSIM, contact your carrier before trying these steps and ask for a QR code to set up your eSIM again.

1. From your device's Lock Screen, try to enter your passcode five times until the "[Device] Unavailable" screen appears and your device asks you to try again later.

2. When you're able to, continue to enter your passcode until the "Security Lockout" screen appears and you get the Erase [Device] option in the bottom corner of the screen.
 3. Tap Erase [Device], then tap Erase [Device] again to confirm.

4. Enter your Apple ID password to sign out of your Apple ID on your device.

5. Tap Erase [Device] to permanently delete all of your data and settings.

6. When your device restarts, follow the onscreen instructions to set up your device again, restore your data and settings from a backup, and set a new passcode.

You can only reach the "Security Lockout" screen if you have an active cellular or Wi-Fi connection and previously enabled Find My ( Find My - Official Apple Support ) on your device. After you try to enter your password ten times, your device will either erase itself or show Security Lockout and the option to Erase [Device] without a timer, depending on how you previously set up your device. 

If you can't follow the above steps (e.g., you are using an older iOS version), you can use a computer to reset your device, as described in this article --> If you forgot your iPhone passcode, use your Mac or PC to reset it - Apple Support .

Whichever method you use will result in erasing the iPhone. You have no alternative. You can, however, restore it from a backup as described in this support article --> Restore your device - Apple Support Some items will restore automatically once you make sure you are signed into iCloud (if you were using iCloud to sync these services).

Here are resources if you are prompted for your username and password and have forgotten them:

If you forgot your Apple ID - Apple Support Note that typically this is an email address you use.

If you forgot your Apple ID password - Apple Support

If you do not have a computer, use the link Find Locations to find an Apple service location, or ask a friend if you can use theirs. This could be either a Mac, or a PC with iTunes. If your computer doesn't recognize your iPhone, iPad, or iPod, read this support article --> If your computer doesn't recognize your iPhone or iPad - Apple Support

If you reset your passcode in the last 72 hours and have forgotten it, read this article about a special reset service available in iOS 17 and higher. --> Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support