Here’s a video about 3 Nephi 20–23.
The people must have been eager to hear anything and everything the Lord had to share during His brief time with them. He taught them about many things that related to their daily lives—how to be baptized, administer the sacrament, avoid contention, live the gospel, and so forth—but He also told them about things that would happen in the future.
We are now living in the time Jesus talked about in these chapters! He is actively gathering Israel today, and when we share the gospel, keep our covenants with the Lord, or do temple work, we help! What a privilege it is to help the Savior fulfill the promises He made to people in the ancient Americas all those years ago.