Unfortunately, that{s not going t be the easiest thing to do.
You can create a new Apple Account at https://account.apple.com
click here ➜ How to create a new Apple Account - Apple Support
Once its created, you can go into your devices and log out of the shared account in Settings ➜ Account, Settings ➜ Account ➜ Media & Purchases, Settings ➜ Apps ➜ Messages ➜ Send & Receive, and Settings ➜ Apps ➜ FaceTime ➜ You can be reached by FaceTime at and sign in with the new account.
Once that is accomplished, then you'll have the tedious task of deleting messages, photos, files contact ec... that you don't want and keep what you want.
Also, if you wish to continue to share purchases, you will need to enable Family Sharing.
click here ➜ How to set up Family Sharing on your iPhone, iPad, or Mac - Apple Support
Also, any apps downloaded with the other Apple ID will remain tied to it and continue to require that password for updates. You can delete them , and re-download them with your new Apple ID.
Family sharing will allow you to share paid apps and apple subscriptions, but most third party subscriptions will not be shared over Family Sharing.