Alma is perhaps a little less clear here than he has been before. He has argued that the fall required the human ability to die, so that the mortal state might be changed. He is now arguing that, after Yahweh provided for the atonement, it was important to tell human beings about it.
After the fall, Yahweh sent angels to teach Adam and Eve about the plan of redemption (Moses 5:6–8). After creating the conditions for the fall and the conditions for redemption, Yahweh therefore informed Adam and Eve what had been done and what they must do. This step constitutes the revelation of the gospel to Yahweh’s children.