Ionic Config api

I do not understand how to use the config api that is listed here:

Particularly this example below:
config.set(‘ios’, ‘favoriteColor’, ‘green’);
// from any page in your app:
config.get(‘favoriteColor’); // ‘green’ when iOS

What are my imports? Can I do this in the app.module.ts? Also, the documents read that if I don’t say the platform then the variable is available on all platforms, what would the syntax look like then?
config.set(null, ‘appName’, ‘App’)? config.set(‘appName’, ‘App’)?