I can not erase the current Apple ID to enter my own. How do I do this?

If this is a used device, you will need to contact the previous owner to have them log out of iCloud or go to https://www.icloud.com/find/ My Phone and erase the device, then remove it from their account. If you can’t do that, the device is useless. 

Turn off Activation Lock - Apple Support.      

If necessary, if you are the original owner, contact Apple ID Support. Apple Support will need to see the original purchase receipt with the serial number/paperwork.

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.  (Link doesn’t always load)   

Get Support      Work through the screens to get a chat option. 

https://twitter.com/AppleSupport

First, sign out of Find My. Second, sign out of the existing Apple ID. Third, sign in with the new Apple ID.

1. Get help with Apple ID
2. What to do after you change your Apple ID email address or password - Apple Support