If you want to only update Kodi which is an app you just need to download other versions available and then install them on the box.
For example if you want to install Kodi 15.2 you will need to uninstall Kodi 14.2 and then download Kodi 15.2 and i=nstall it on your box.
Here is how to uninstall Kodi: Settings> Apps> Kodi> uninstall
Then download Kodi 15.2 from the below link: https://