Hello, I don't know where to put it. Tried a number of locations, but get different error messages e.g. "Type 'Void' cannot confirm to 'View'. Where should I place FirebaseApp.configure()? Thank you for any suggestions.

Hello, I don't know where to put it. Tried a number of locations, but get different error messages e.g. "Type 'Void' cannot confirm to 'View'. Where should I place FirebaseApp.configure()? Thank you for any suggestions.