Yes, you do.  You’ll enter your credit card (on the web version) or sign up through the app (Apple or Google). The App Store or GooglePlay already has a card on file.  While you might get a receipt that says “thanks for your purchase”, it’s $0 until the trial period is over.  Then, if you choose to continue, the yearly fee will be charged. However, you can always go into the app, at any time, and adjust the auto renewal settings however you like.