You need to be clear on how things are setup by default and what can be changed.
If you are using the standard routes then there is a directory app/ controllers where your controller files *.rb live. There will also be a directory app/views/<controllername> for the *.rhtml and *.rjs and *.rxml files that go with that controller. For normal operations there will be one of the above files for each action on each controller.
The URL you indicated /admin/news would indicate admin as the controller and news as the action. If news is really a controller the URL would normally be /news or /news/<action> with index being the default action.
I would recommend the book Agile Web Development with Rails as it has a very fast intro tutorial in the first few chapters to get you oriented, then goes into everything in more detail. The book is well written and easy to read.
Michael
