What did King Benjamin say we have to do to retain a remission of our sins? We have to give to the poor (Mosiah 4:26), and Amulek taught that too. If we want an answer to our prayers, if you want God to give to us, we have to give to others. Did Alma and the sons of Mosiah do that? They did, in a remarkable fashion. They taught and they suffered persecution, no doubt in part to show the sincerity and completeness of their earlier wickedness and damage to the church.
In verse 33, Alma and the sons of Mosiah "impart much consolation to the church." What were they doing? Restitution, reconciliation, and repentance. They were trying to console and reassure the believers. They were asking for forgiveness. It was the church that they had put in an awkward position. What did they do next to confirm their faith? Not only were they saying, "We were wrong," but they were also saying "you were right." They were "exhorting them with long-suffering and much travail." They had been teaching, "Do not bother keeping the commandments." Now they wanted the people to be sure to keep the commandments.
In verse 35, we see them zealously striving to repair the spiritual damage they had caused. They were also confessing. Is confession an important part of the repentance process? Absolutely. It does not say to whom they confessed their sins, but I imagine as part of consoling the church, they were confessing to the church.
With their conduct, they may also have been implicitly confessing to Alma the Elder, the head of the church, because, after all, a lot of the things they did had been in secret (see Mosiah 27:10). That may have been helpful information for Alma. It might have been pretty shocking. He must have known that things were bad with his son, but he may not have known how bad.
In verse 37, "they did publish peace; they did publish good tidings of good; and they did declare unto the people that the Lord reigneth." Does that remind you of one of the questions that Abinadi answered (see Mosiah 15:13–18). Alma the Younger probably had learned these word from his father, who had been converted by the testimony of Abinadi. And who will be the ones to proclaim peace? Is it just the one messenger? Is it just the Messiah? Abinadi taught that it was all the holy prophets (15:13). So Abinadi had certainly laid the groundwork for these five friends to publish good tidings of good. This is part of the repentance process, to help other people by proclaiming to them the peace of the Living God.
Book of Mormon Central, "Why Would Noah’s Priests Quiz Abinadi on Isaiah? (Mosiah 12:20–21)," KnoWhy 89 (April 29, 2016).