Major Newbie Needs Major Help!

Hoping that the community can help me out.  I'm a major newbie to RubyMine, and Ruby in general and need some serious assistance in just getting past 'Step One' of my initial goal.  Goal:  To make a simple change in my existing code repository and then see and test the change.  This is where I've gotten so far:  Successfully installed Git on my laptop.  Successfully installed JetBrains Ruby and RubyGems as well.  Have replicated the existing code respository from 'Github' without a problem and can see all the code in JetBrains Ruby.  This is where the 'newbie' gets stuck.  I want to make a very simple change, just to understand the overall process.  So, for example, add the word 'The' to my websites footer.  How do I make this edit (think I can figure this one out pretty easily, but just in case), test the edit and then view the change?  Another way of looking at it would be...if I make a change to a .html based website I can easily view and test that change via a browser preview, how can you make, view and test a change in JetBrains?  Thanks Everyone!