If you integrate your product with your Feedback account, following the steps here, then your customer data will be automatically added to Feedback.
Once you expose a link to customers, they can then log in to Feedback through the widget or a link to the portal, depending on which option you chose.
If you don't want to integrate with Feedback, or want to get started in the meantime, it's possible to manually invite customers into Feedback.
Note: This isn't recommended for a long-term solution because your customer data won't be automatically updated and customers have to manually login to Feedback.
You can do this by following these steps.
You can set up SAML SSO to enable your customers to log in to Pendo Feedback without a username and password.
Follow the steps here to get set up.