Visit the MBTA's commerce page to order your Charlie Card. Click "Buy Stored Value on a Charlie Card". Click "Buy Now" next to the card of your choice. You can choose a card preloaded with $5, $10 or $20. Click "Checkout" then sign into your MBTA account. If you don't have one, click "Register" and use your email address to register. At the checkout screen, enter your credit card information and complete the order. Expect your Charlie Card to arrive within one week.
Find your local subway station and speak with a representative at the MBTA customer service desk to buy a Charlie Card. This is also available at some bus terminals.
Locate your nearest MBTA "T" (ticket) office to purchase a Charlie Card. See the ticket office locator to find a ticket office close to you.