Make an existing user part of Administrators

[Gianluca Cecchi]

Hi,
I don't directly get ml e-mails in my inbox and I see that Bill Oliver
post is empty at archive link:
http://lists.fedoraproject.org/pipermail/users/2012-November/426712.html

I only see some references to his reply (such as install doc link) in
other users' replies...
It would also be good to see the "other things" as written by Matthew Miller:
"
... many things in the distribution, including sudo,
consolehelper, and policykit, are configured to understand that this means
that the user is an admin."

The sudo part is simple but the other ones?
Any graphical way after install to make the same thing?

Gianluca