AppPresser apps come with a registration form that allows users to sign up quickly to get a login for the app.
When they sign up, the user is added to your site as a Subscriber with a meta value of app_unverified = true. They are sent an email with a verification code, which they can enter into the app. This removes the app_unverified meta value and allows them to login to the app.
To allow users to register (free) in your app, visit Login Settings tab and check "Allow users to register" and enter the URL as prompted.
You must have a WordPress URL set in the login settings.
The registration form will only show in the app login modal, so you can add the login button to the side menu as shown above, or add a menu item that opens it.
Custom Registration Form
If you want a custom registration form, add the url under WordPress Registration URL. Note that this must be https, on the front-end (can't be register.php or any admin page), and it bypasses all the functionality mentioned above.