How can I copy an iMovie onto a USB stick?

I recently filmed an assignment on a video camera, which a friend then copied onto a USB stick. I then installed the Smart Converter App because the files could not be recognised by my Mac. By some miracle, the files got converted and I was able to play them (Quicktime) through iMovie. Once I got to this point, I have found I can't copy this iMovie back onto a USB in its edited form. I am unable to share my movie onto YouTube due to privacy issues, the files are too big to attach to an email and it is also too big for iCloud. All I need a is a freaking way to copy this back on to a stick. Please...someone! Tell me it can be done! And please use really simple language...I'm hopeless on computers!