Out of the box, CRM 2013 business process flows have a set of default stages. Often times, these default stage values are not relevant to the business process you are trying to implement. So how do we change these to something more pertinent?
The process is very simple and similar to the process of customizing a global option set in CRM.
First, go to Settings > Customizations and click Customize the System.
Then click on Option Sets on the left. Open the Stage Category option set in the list.
Now, you can customize the available stages just as you would any other option set.
Follow these steps and you will find that modifying the stage category for business processes in CRM 2013 is quite simple.