As soon as the last ticket is bought, the draw is automatically made.
5 winning numbers for that specific jackpot are randomly chosen and the respective users credited.

You'll be able to see the last 5 jackpot draws for each type on the bottom of the jackpot page.

If you're one of the winners, you'll see your username highlighted in the winners list and you'll get an entry in your history log (beside the prize, obviously).