This videos teaches how to add a module to an Angular Application using Angular CLI. We can also do that manually but to do it using CLI, we use the command:
ng generate module module-name
There is an alias also to it.
ng g m module-name
This will add the module to your angular application which is the step one of adding the module.
To register the module inside the app module, we need to do step two of the process which is by adding another command:
ng generate module module-name -m=app.module
This video explains the whole process in detail.