You ll find the Terminal in the Utilities folder within the Applications folder. To carry out any of the following commands you will need to copy/paste or type in the line of text then hit enter. For the most part, applications will need restarting before changes take place. For most applications you can just quit and open them again, and for the Finder you can use the Force Quit dialog, just log out and log in again or type "killall Finder" into the terminal after the command.