How do I update a Navcore on a one new edition V4

I have spent hours looking around the tutorials trying to find a definitive set of instructions on how to update my Navcore.

I would like to try 9.541 but don't know how to update it, I originally did this with my current config back in 2011, when detailed instructions were available on this site. now a lot of the links that might be helpful in threads are dead.

can anyone please direct me to a relevant page/s on "How to's" that is current.