If your postcode wins the Main Draw (on the homepage) you will see a box appear with a big "Collect" button.
If your postcode wins on the Stackpot, the block will be green. Click it to claim.
If your postcode wins on the survey draw you will see a large "Collect" button.
Once you have claimed the FPL team are notified of your email address, win amount and bonus at the time of the claim. Payments are made via PayPal's Send Money service to your email address.