Alma 17:8

and thus they departed into the wilderness, with their numbers which they had selected, to go up to the land of Nephi, to preach the word of God unto the Lamanites.

So they went into the wilderness with the men they had picked. They went up to the land of Nephi to preach God’s word to the Lamanites.

They headed into the wild with their small group, traveling up to the land of Nephi to preach God’s word to the Lamanites.