Alma 34:16 - 34:20
Alma 34: 16 And thus mercy can satisfy the demands of justice, and encircles them in the arms of safety, while he that exercises no faith unto repentance is exposed to the whole law of the demands of justice; therefore only unto him that has faith unto repentance is brought about the great and eternal plan of redemption.
So the individual who repents of their sins can have the justice that sinful acts requires can be satisfied by the atonement. But the individual who does not repent of their sinful acts will have to pay for their sins themselves. The atonement cannot be evoked on their behalf. Again the atonement only applies to those who repent and have faith in the gospel and its power to save.
Alma 34: 17 Therefore may God grant unto you, my brethren, that ye may begin to exercise your faith unto repentance, that ye begin to call upon his holy name, that he would have mercy upon you;
With the instructions that Alma has given these Zoramites, Amulek now encourages the people to begin to pray that they might gain the faith which will motivate them to repent of their sins, that the Lord can mercy on them because they have gone through the steps of repentance.
Alma 34: 18 Yea, cry unto him for mercy; for he is mighty to save.
Indeed ask the Lord for mercy as you repent. He dearly wants to give to you.
Alma 34: 19 Yea, humble yourselves, and continue in prayer unto him.
Realize that one is weak and needs help in the struggles of mortality. So continue to pray to ask for help in all things.
Alma 34: 20 Cry unto him when ye are in your fields, yea, over all your flocks.
Pray not only for your own efforts to live righteously, but over your fields and flocks that they will be able to give the support one needs to live.