Deploy your app to App Engine, so that anyone can access your app in the cloud. You will need to register a project and obtain the Project ID, as this will determine the web address for the app.
In the Cloud Platform Console, go to the Projects page and select or create a new project.
Note the Project ID of that project.
Deploy your application to App Engine, using the above Project ID as an argument:
gulp deploy --project=<YOUR_PROJECT_ID>
When finished, your app will be ready to serve traffic at