The plugin creates a WordPress account for each member when they pay. It uses their email as the username and randomly creates a password for them. Then it emails them their username and password.
If you need to reset a users password, in your WordPress admin you can go to Users and search by email. When you click on a user, near the bottom of the page you can reset their password.
You can allows users to change their own passwords.
In the settings page for the plugin, on the tab “Subscriptions” there is a setting for “Admin bar”.
If you set that to No, then the customers will see the admin bar at the top of the page. They can click their name on the top right corner of the screen and view the WP admin page. However because they are only a subscriber and not an admin, they can’t do anything but edit their own account / password.