The Publisher's Clearing House activation code can be found on the back of the postcard that arrives in the mail. The five-digit code is in a black and orange box located right under the instructions on the back of the card.
Once a recipient receives the code, the recipient can enter the activation code at the PCH's Activation Code Input Form page, where it says "Enter Code Here." When the code has been validated, the recipient needs to answer a few more registration questions before registration is complete. Registering with PCH allows people to enter the company's Fast 50 Sweepstakes.