Just click 'GET FREEBIE', be sure you "allow pop-ups" so that you can enter your details in the pop-up that will appear after a few seconds on the website. Enter your details and make sure you agree to receive free samples in the future so you can carry on getting all the best Clarins cosmetics!
It should arrive to your door within 28 days.
If you don't see the popup form, try it on another mobile or laptop and it should show up. You could even try using a private window on the same device.