Hi @charles_lim ,
The initApp should be placed in the initialization logic of your app. I recommend you to start with a project template that can be downloaded from Backendless Console:
Step 1:
Step 2:
Step 3:
This will download a zip file that contains Angular project structure.
The initApp call will be already included in the app.components.ts file.
As for your-subdomain-name, you can read in the docs at:
https://backendless.com/docs/js/setup.html
Regards,
Mark