How do you teach an Atheist about God, where do you start?
Convince him to read the Book of Mormon. After he has done that, ask him if he will read it one more time. This time sincerely apply the instructions given by Moroni in Moroni 10:4—
And when ye shall receive these things, I would exhort you that ye would ask God, the Eternal Father, in the name of Christ, if these things are not true; and if ye shall ask with a sincere heart, with real intent, having faith in Christ, he will manifest the truth of it unto you, by the power of the Holy Ghost.
Then promise him that if he will follow those instructions and sincerely ask the Father if the Book of Mormon is true as he begins to read each page–we’re talking about 531 prayers– before he finishes the second reading he will know with an unshakable surety that the Book of Mormon is indeed true, and he will no longer be an atheist.