If you would like to sell your Magazines present in the App via subscriptions, a Shared Secret keystring is required.
To acquire the Shared Secret keystring please follow these steps:
Log in to your App Store connect account (https://appstoreconnect.apple.com/login)
Open the “My Apps” Tab and select the App entry that you would like to edit ( For this example the Yumpu APPKiosk Test entry has been used )
Next select the “Features” tab in the upper left corner
Click on the entry called App specific key (shared secret) in the Window to the right and copy the Code that will be shown in the pop up.
If no entry is present yet, a new one can be created by clicking on the respective option in the Pop up.
If a Master Key ( Master Shared Secret ) is already present in your Account it can be displayed by clicking on the "Show Masterkey ( Master Shared Secret )" option.
Enter the code shown into the App information form of your APPKiosk entry in your Yumpu Useraccount afterwards.