To allow all users who have an account within the app access, select Yes on Allow all the users by default.
To authorize your users manually from the Users menu, select No on Allow all users by default.
Accounts must be manually specified to access the Locker in the Users menu (located in the left menu bar):
Other Settings
Select Yes on Lock the entire application? to block the entire app (i.e. a private app).
Use this to force your users to create accounts with both Allow all the users by default and Lock the entire application set to Yes.
Select No on Lock the entire application? to block individual features.
If No is selected, check the features under Choose the features to lock.
Before submitting an app, create a user (without mentioning “test” or “demo”) with authorized access. Then, when you publish your app on iTunes Connect just fill out these info in the user demo fields to let Apple reviews what is behind the padlock feature.
Background
Use the Background tab to change the background of the Padlock feature: