Tell the printer to print in duplex mode. Depending on the make and model
of your printer you may have to take the paper from the out tray, reverse it
and put it back in the sheet feeder. It's the soft of information you will
find in your printer manual. Should you have lost your manual, a PDF copy
is usually available at the printer manufacturer's website. ALL printers
are different so there is no standard one single answer to this question.