When you see the instruction to "run ... in the terminal" or "in the console" or "on the command line" or "the command prompt", it means to open the Terminal Emulator (or similarly-named) program from the Applications Menu and type (or paste) in the given command. Pressing Enter will execute that command, printing out any textual output the command might give, or errors. If you want to learn more about the all-powerful terminal use, try one of the free Unix command line tutorials.