Mosiah 28:9

and they took their journey into the wilderness, to go up to preach the word among the Lamanites: and I shall give an account of their proceedings hereafter.

They started their journey into the wilderness. They went to preach the word to the Lamanites. I will tell about what happened to them later.

They set out into the wilderness to preach among the Lamanites. I’ll tell you what happened to them later.