If their 'god' isn't Jah, their god is NOT the only one, true, living God, Jah Ras Tafari. You can only plant seeds, or water ones that were planted, and pray for them. Jah does the harvest and opens their eyes. You can plant seeds of thought, depending on their background.
If their 'god' is a white Jesus with blue eyes, and having angels that look like men but have wings on their backs, they believed the great lie spoken of in II Thes. 2.
If their God is the white Jesus, email me email@example.com and I can send a few emails I wrote to another that explain. If their God is the white Jesus, then have them read John 14 and 16 where He told disciples He would send the "Spirit of Truth" as their comforter to guide them in all fullness of joy in life. THen have them read Acts 2, when that spirit came to man, and devout men from every nation on earth understood the kingdom of God that came, in their own native languages, beacuase no language is really needed to understand. He who feels it, knows it, no words needed to explain it.
Later, councils of men organized religions based on the teachings, but God is spirit, not a physical place. Religions work in physical world. Jah is in the spirit world. KJV and others have same OT in all bibles, but there must be other NT writings besides the ones in the KJV that were written by Jews. Considering devout men from every nation understood, then obviously the KJV NT is not the only NT.
If they believe in that white Jesus, but are open to knowing the truth, the Kebra Nagast is a MUST READ for them to open their eyes.
Blessings in Jah