Please refer to this help topic: Sign your app—AppStudio for ArcGIS (Desktop Edition) | ArcGIS
The first two files that you are referring to are provided by Apple when you sign up for the Apple Developer Program. You need these files to sign your application and release it in the App Store.
The URL Schema is added to your app and can then be used to launch your application using a weblink or another app.
The Bundle ID is a unique identifier fro your application. There is a default ID set in AppStudio, but you will need to make sure that your bundle ID and your developer certificates are using the same name.
Use the Advanced menu in the Settings tool to configure these options.
Hope this helps,