After you have understood the idea and terms, click on the checkbox and then the "Connect with Stripe" button.

If you already have a Stripe account, you can simply login and proceed. Otherwise, fill in your contact details in the form. In the website field you can fill in either your personal website if you have one, or the address to your Ziney user index, which you can retrieve by going to "My Boards" and copying the address from the browser URL bar. After everything is correct, press "Authorize access to this account". You will be redirected back to Ziney when the process completes.