Plugin PopUp by Supsystic

Hello,

I am learning how to use popup window for gaining subscribers. A friend helps me out with testing it. He subscribed with his e-mail, but I can’t erase his mail from list to make another test with his e-mail.
Is it possible to edit list of subscribers? There is a .csv excel table, that is read-only. Is it possible tu unlock it and edit it (deleting existing email addresses)?

Thanks!