xterm doesn't support right-click copy-pasting.
please use lxterminal instead.
iirc, lubuntu even has a terminal icon on the panel.
if not, the terminal (it is probably not called lxterminal) is there in the menu under accessories, utilities, system or... you will find it!
and you will notice that it looks different from xterm once you open it.
enter the command there, highlight with you cursor, right-click => copy, and paste here.