As has already been said, what operating system are you talking about.
With Windows, you can change the password of the admin account(s) by simply going into the accounts and going to the appropriate settings. If you use a Microsoft account, then this has to be done on the online account then on the actual computer account. If you use a local account then it is only the computer setting that needs changing.
Changing the account name normally involves creating a net Admin account, then copying over settings and files from the old account and finally deleting the old account.
In Linux, there is one admin account called 'root'. You change the password in the normal way, but the name remains. You can set up some other accounts with similar privileges, but this is not recommended.
I hope this helps.