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
For non-touch-screen printer models, press 
to navigate through the settings.
Select Copy To, and then select the paper source that contains the letterhead.
If you loaded the letterhead into the manual feeder, then navigate to:
Copy To > Manual Feeder > select a paper size > Letterhead
Copy the document.