For that you need to claim your feed, which is easy to do: Click on the “Claim your feed”-link which you find under question 2 in the plugin’s settings page (next to the email icon; make sure you have the email-icon selected under question 1 so that the email icon shows up under question 2)…
…which will ask you to sign up (or login). After you’ve done that, you’ve created an account with your feed, and you can click on “My Offered Feeds”…
…and then on “Add & View Subscribers” which will download a csv-file containing the emails of your subscribers.
While you’re logged in, also click on “Edit Feed” (see the icon on the right in above screenshot) and give your feed a proper description so that more people will find it and subscribe.
