Yes. A card is needed to start the 7-day free trial. You won't be charged if you cancel before the 7 days are up, and you can keep watching until the trial ends.
To cancel during your trial, see How do I cancel my Vooks subscription?
If you don't cancel, you'll be charged for the plan you picked when the trial ends: $9.99/month, or $69.99 for the annual plan. See How much does Vooks cost?