How to access text field labeled "Reason for Loss" when Deal Stage is set to Closed Lost?

How to access text field labeled "Reason for Loss" when Deal Stage is set to Closed Lost?

When we mark a deal as Closed Lost, a Verify Details pop up screen appears and lists 4 fields:
Amount
Closing Date
Stage
Reason for Loss

I want to create custom categories and reasons so that I can provide our internal teams with information about why a sale is lost.  

I'm assuming I can do the same for Closed Won Reasons?