See How to create a new Apple ID https://support.apple.com/en-us/HT204316 See the data implications below.
Some of these things will apply to your situation even though you are not changing your Apple ID: What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071
Keep in mind that some things available under a first Apple ID will not be available under a new Apple ID. For example, you won’t be able to transfer anything purchased from the App and iTunes Stores to the new ID. And, there are other issues to be addressed.
And see what Eric Root says on this matter here https://discussions.apple.com/thread/251343949 and
what Winston Churchill says about it here: https://discussions.apple.com/thread/7452747