I’m assuming you’re on Windows.
Press the Windows+R combination, write “cmd” (without the quotes) and press enter. What you’ll see appear is the command-line. It is used to run many different commands. A commandline or terminal is preferred by programmers over a graphical interface. All of the commands you’ll see in butler’s documentation is what you need to type in the commandline (the commands are those that start with “butler “, without quotes again).