Sure. In the main application.html.erb of your site, you should see this line somewhere in the <head>:
<%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>
If you don't, then that's because you moved it into a partial (called rails_defaults, maybe -- that's what I recall from your first post).
You can use any script name you like here, application is the default, where by convention, all of your other scripts are "rolled up". That's done by the file /app/javascripts/application.js, which culminates in the line
//= require tree .
which slurps up all the javascript files in the /app/assets/javascripts directory that are not already loaded by previous require directives in application.js, and concatenates them into the one published file.
A generic (rails new ...) generated site will have all of this done for you, so I recommend you try building a new stunt site from scratch and see what gets built for you. Try building a new app, then inside that, using the scaffold generator to make a couple or more models:
rails new test_blog
cd test_blog
rails g scaffold Post title body:text slug
rails g scaffold Author name email
rails g migration add_author_to_posts author:references
rake db:migrate
rails s
navigate to http://localhost:3000/posts
Everything you see will be run through the asset pipeline, although the full concatenation will not be there in development mode.
If you add some JS to the app/assets/javascripts/authors.js and posts.js, and refresh your browser, you should see those scripts appear in your browser's Developer tools when you inspect the DOM. In development, each file will be listed separately, as coming from /javascripts/posts-asdfsdfsdsdfsdafsdfsdafsd.js or similar (32 character hash, which is the MD5 of the file itself, is appended to the filename).
To see how this would work in production, you would first run:
rake db:create RAILS_ENV=production
rake db:migrate RAILS_ENV=production
rake assets:precompile RAILS_EN=production
and then when you started the dev server with the production version:
rails s production -p 3000
you would see all of the JS and CSS concatenated into application.js and application.css respectively. None of the individual files would appear at all. The whole thing will be minified and concatenated.
If you require some files in order in application.js, then only the files you don't require by name would be auto-loaded by the greedy require_tree operator. You might do this if you needed to specify that jQuery load before something else that needs it, for example. But otherwise, the files will be concatenated in alphabetical order and then minified and gzipped into one application-someMD5hashgoeshere.js file. The javascript_include_tag helper knows how to find that file and load it.
Walter