Your ignorance is, unfortunately, a lot. NHF
NG is abbreviation for NextGen. All NG versions works on Oreo. Try for example PAL, it is latest.
I think you did not read either Rules or Announcement. If you were, it would be clearer what would affect the installation.

Phone and HU are different devices. So usually setups differ. In every post there are clear instructions how to setup iGO from internal memory.
In the continuation of the topic there are discussions and versions that run from the external SD card. But, not possible on all devices.
Of course, you need a little basic knowledge of working with Android. Use third-party file manager. Set your device. Use google search.