Ok, we need a window to work in.
If you logged into a Mate Session or a Gnome Clasic then somewhere either at
the top or bottom of the screen you should see an icon that looks like 
.
Point and mouse click the icon to bring up a terminal window.
If you do not see the icon, then look in the menus 
(top or bottom left corner of screen). In the APPLICATIONS->SYSTEM TOOLS menu, look for the icon
or application named TERMINAL.
If you are using the new Gnome Session, then you may want to search for terminal. Once you open the terminal, the window will be labeled with 'xterm' or your login name@machine name followed by the current directory.
You can establish an icon in the menu bar or desktop. You can bring that window up at any time by clicking on it. Another thought, you can open up multiple terminal windows which makes it useful when you are working on a multi-file application.
Inside the window, you will see a similar label inclosed in [] followed by a flashing cursor. This is call the system prompt. Whenever I ask you to "type the command...", do so in the terminal window at the system prompt. Specifically, during the tutorial, when you see text in the bold font, type the text exactly the way in appears at the system prompt in the terminal window. exactly!