Q: edit administrator account

System Preferences --> Users & Groups

• Make sure the administrator account is highlighted on the left-hand side and click the padlock in the lower-left corner, inputting your password
• Right-click on your highlighted administrator account, selecting "Advanced Options."
• You'll see something for "Account name" and "Full name."  Pay attention to the warning at the top of the dialog box that comes up, making whatever changes you want to make.  When you're done, click OK, then restart your computer so the changes can take affect.

With a lot of care!

The 'full name' can be edited by unlocking & editing it in 'System Preferences > Users & groups, select the user' and change it.

The 'short name' is more complex - if you do it incorrectly you can break the user account. It is used for the home folder name etc. You need to have another admin account to do this correctly.

Apple have this info on the topic…

Change the account name and home directory name on your Mac - Apple Support

Read it before you begin.

Or this covers it for 10.6, 10.7 is the same with different looking buttons…

http://mmug.org.uk/extra/changing-account-name-mac-os-x-106

Both of the above are good considerations.

When setting up a machine, plan on the main account being an over-seer and it need

not be much more than Admin User. That need not change even if the computer is

used by several people because they'd have a Standard account or use Guest login.

• OS X El Capitan: Set up users on your Mac

A second Admin level account could be created, if the computer does not automatically

login to an administration-level account; there is where security begins, if the login screen

is where any visitor to the computer happens across it. And if it is physically secure too.

This hasn't changed much over several OS X versions; short name is also addressed:

http://osxdaily.com/2007/02/15/changing-your-macs-computer-name/

Then there are other methods that can use single-user mode to change admin password.

http://osxdaily.com/2011/04/25/change-admin-password-mac/

and host name http://osxdaily.com/2010/09/06/change-your-mac-hostname-via-terminal/

About passwords:

• Change or reset a user account password on your Mac - Apple Support

View other similar content in Apple Support Communities:

https://discussions.apple.com/article/HT1428

Be careful or you may have more fun than you bargained at a later time.

Good luck!