Alma 21:4

And it came to pass that Aaron came to the city of Jerusalem, and firstly began to preach to the Amalekites. And he began to preach to them in their synagogues, for they had built synagogues, after the order of the Nehors; for many of the Amalekites and the Amulonites were after the order of the Nehors.

Aaron came to the city of Jerusalem. First he started teaching the Amalekites. He taught them in their churches. They had built churches following the teachings of Nehor. Many of the Amalekites and Amulonites followed the teachings of Nehor.

Aaron arrived in Jerusalem and started preaching to the Amalekites. He taught in their synagogues—they had built them following the teachings of Nehor, since many of the Amalekites and Amulonites followed that order.