As a point of conjecture, I believe that Alma the younger received his CE when the angel appeared unto him the second time in Alma 8:15
" 15 Blessed art thou, Alma; therefore, lift up thy head and rejoice, for thou hast great cause to rejoice; for thou hast been faithful in keeping the commandments of God from the time which thou receivedst thy first message from him. Behold, I am he that delivered it unto you."

23 And it came to pass after they had fasted and prayed for the space of atwo days and two nights, the limbs of Alma received their strength, and he stood up and began to speak unto them, bidding them to be of good comfort:

24 For, said he, I have repented of my sins, and have been aredeemed of the Lord; behold I am born of the Spirit.

25 And the Lord said unto me: Marvel not that all mankind, yea, men and women, all nations, kindreds, tongues and people, must be aborn again; yea, bborn of God, cchanged from their carnal and dfallen state, to a state of righteousness, being redeemed of God, becoming his esons and daughters;

26 And thus they become new creatures; and unless they do this, they can in anowise inherit the kingdom of God.