G'day Stellaris, Welcome to Linux.org
As well as the info asked for above.......what is the command you typed in?
Did you type it in or copy and paste it from somewhere?
Did you then tap the Enter key?.....if you did, what response did you get?
If you did not, then try that, and inform us of the response, if any.
Thanks David, I have just seen your response.......tap the enter key (after going back to the terminal screen)