Right-click the topmost panel of your display, then select Add to Panel.
Look for the Quit symbol. Select it by Left-clicking on it. Then
click on the + Add button, and then Close.

Who would have thought that a linux distribution would have a simple
solution to a problem!

I know you may be frustrated by using Linux. I understand. I started out 5
years ago
and screamed out so many words in anger of it. However, I was not going to let
Linux
beat me. I held my ground and learned on how Linux works. It is a not at all
like Windows and that is what a lot of new users of Linux get pissed off at. The
new user who sees all the fluff and glitter on line on Linux. They want that
kick butt desktop. To get that kick butt desk top takes work. It can be done.
However, the new user just wants it to do the things it did when the user was
running windows. Like get on the internet and then see that all not the bells
and chimes play. Like flash player or Java.
Do get down to the to it. I give you some links to help you understand. All I
ask you is give Linux a try. And you'll see why Linux act differently than
Windows.
Lesson # 1.
http://linux.oneandoneis2.org/LNW.htm
Lesson # 2
video.google.com/videoplay
Lesson #3
video.google.com/videoplay\

Well, you can use the command line or you can use a button...

The command line is:
sudo shutdown -P now

or

sudo reboot

The first will totally power down, the next should reboot you.

However, if you have a gnome panel up and going, you should be able to
right click on the panel and choose "Add to Panel..."

Then select the item titled "Quit..."

Once that is added to the bar, it will allow you the same access to the
shutdown, logoff, restart, hibernate, and suspend scripts as well as
lock screen and such that you are used to.