Inserting credit card details is not mandatory to begin the 7-Days Free Trial on the Premium Plan Subscription. Nonetheless, it is recommended to insert your credit card details to ensure continued access to the Premium Plan features when the trial expires.
Do note that, if no credit card details are provided within the 7-days trial, your Project will be downgraded to a Free Plan when the trial expires. You will be able to retain all Project content and data.
To continue the Premium Plan subscription when the trial expires, simply insert your credit card details anytime within the 7-days trial.