Turn on your printer.
Visit the website of the airline you booked your flight with.
Look for the "Itineraries" or "Check-in" option. Choose to check in online.
Enter your confirmation number located on your ticket that was emailed to you. Some airlines give you the option of entering the credit card number you used to pay for the ticket instead of the confirmation number.
Click "Select Seat" or something worded similarly. You can also upgrade your seat for a fee or check in additional baggage.
Locate the "Print Boarding Pass" button. The exact wording may vary for each airline.
Click the "Print" button.