Understanding the NESI Software
The latest version of the NESI software can always be found on the NESI GitHub. Not only will you be able to use the most up to date version but you can also find preceding revisions of the NESI software. To download the software click on the "Download Zip" button in the lower right hand corner and save it to the directory of your choice. Once the code has been downloaded to your computer you can upload it into MPLAB X by following the same steps as in the Software Development Environment Test video.
Reference Code Modules to learn more about the NESI board API.
MPLAB X Debugging
This MPLAB X Debugger video is very informative in how to use the debugger for Michrochip's MPLAB X. I highly recommend watching it at least once if not more to get a good understand of how useful this tool really is.