reboot with sudo?

[Sanh Duong]

I'm a new user and I'm trying to get sudo to work on my system.... I
installed it using root and in the / directory... the problem I'm having now
is. how do I set up so that I can shutdown the computer with a normal
user???? I treid doing the: sudo shutdown -r +15 "quick reboot"
but it didn't work cause it said I need to do something with the sudoers???
how do I do that?? thanks...

Sanh.