Nephi and his brother, Lehi, had had great success preaching to previously apostate Nephites, and then to the Lamanites themselves. After those successes, they headed north. Now, Mormon tells us about that part of their missionary journey. It is brief, but important.
Verse 2 tells us that Nephi went to the people in the north, and did what he had previously done with success: he preached the word of God.
Verse 3 tells us what we need to know about the people in the north: “They did reject all his words, insomuch that he could not stay among them.” Even a prophet so great as Nephi could not soften the hearts of those in the north. Once again, Mormon prepares his readers for the eventual destruction of the Nephites that will come at the hands of the Gadiantons who are connected to these unrighteous northern lands.