You can start your 7-day free trial by signing up for a Blinkist yearly plan. You are under no obligation to stay for the whole year and will not be charged until the 7-day free trial is over—just subscribe, learn to your heart’s content, and cancel any time before your 7 free days have passed.
Please note that you may only start a trial once: if you've previously purchased a subscription and made use of the 7-day trial already, you won't be able to start a new trial the next time you sign up for a yearly subscription.