Visit the website of the airline with which you wish to book your frequent flyer flight. For example, visit aa.com for American Airlines, delta.com for Delta, southwest.com for Southwest and united.com for United.
Click on a link that says "Redeem miles," "Use miles" or something similar. Of the four biggest airlines in the U.S., only United immediately offers this link. For Southwest, you must hover your mouse over "Rapid Rewards" then click "Book Reward Travel" from the list that appears. If you see a button or checkbox to click saying something similar, click it. American Airlines and Delta have such a check box.
Fill in the required information to find your flight. This will include departure and arrival cities, dates and the number of travelers.
Select the flight or flights you wish to take, then click "Next" or "Continue." Enter your frequent flyer number and password when the website prompts you to do so. Unlike most other sites, Southwest will prompt you for your number and password before displaying available flights.
Follow the website's prompts to finish booking your frequent flyer flight. At some point, you will need to enter some or all of the following information: traveler's name, address and phone number, a credit card number for any fees, a passport number (for some international flights), an e-mail address and other similar information.
