Load an original document into the ADF tray or on the scanner glass.
From the control panel, navigate to:
Copy > Copy From > select the size of the original document > Copy To > select a paper source
If you are loading into the multipurpose feeder, then navigate to:
Copy To > Multipurpose Feeder > select a paper size > Letterhead
For non-touch-screen printer models, press 
to navigate through the settings.
Copy the document.