Install By Adding a Repository
Navi-X is currently available inside TVaddons repository.
See how to get TVaddons.
Once you have TVaddons at hand, all is left is to install Navi-X itself, like so:
Go into SYSTEM >> Add-ons >> Install from repository, then go inside TVADDONS.ag addon repository >> Video add-ons >> enable Navi-X by selecting it then select Install.