Thank you, that is very in-depth. Where it says:
Rename the administrative account: On a new install you can simply create a new Administrative account and delete the default admin account. On an existing WordPress install you may rename the existing account in the MySQL command-line client with a command like update tableprefix_users set user_login='newuser' where user_login='admin';, or by using a MySQL frontend like phpMyAdmin.
My site is existing. Can I still make a new user, then delete admin and tell it to attribute all posts to the new user? If it is necessary to do it the other way for some reason, I would have to ask my host for help.