[these things which I declare unto you, and which I shall declare unto you hereafter of myself,] “These things” are the content of the message of the Savior to the Nephites, or the record of the events now occurring.
[shall be made known unto the Gentiles that they may know concerning this people who are a remnant of the house of Jacob] The record of these events “shall be made known unto the Gentiles.” They will know of the Nephites. The Savior is saying that the coming forth of the Book of Mormon is a necessary preliminary to the final gathering.