If you were a bad example as a teen and several of the other teens at church were influenced to sin by you, once you have repented and started living as a Christian years later, what does the Lord want you to do? Do you need to track these people down and ask their forgiveness? Will you be held accountable for leading them astray as Jesus said in Matthew?
"For godly sorrow produces repentance leading to salvation, not to be regretted; but the sorrow of the world produces death. For observe this very thing, that you sorrowed in a godly manner: What diligence it produced in you, what clearing of yourselves, what indignation, what fear, what vehement desire, what zeal, what vindication! In all things you proved yourselves to be clear in this matter" (II Corinthians 7:10-11).
In a literal sense, the past is not fixable. You cannot return to the past and change what you have done. You might be able to lessen the impact of your misdeeds. For example, if you had stolen money, you might be able to restore what was stolen as a demonstration of your change. This is what Zacchaeus did. "Look, Lord, I give half of my goods to the poor; and if I have taken anything from anyone by false accusation, I restore fourfold" (Luke 19:8). Zacchaeus knew he had wrongly profited from others. Those he knew he corrected his fault, he vowed to return to them four times what he had taken. The Old Law only required a 20% addition to the return, but Zacchaeus was zealous to prove his change. Yet, there were many whom he could not return what was taken. For this reason he vowed to give half his wealth to the poor. He couldn't make it up to the specific individuals, but he could at least remove his ill-gotten profits and benefit people in general.
You can do the same. Those you may still have contact with, you can call or write a nice note apologizing for your past misbehavior and let them know the peace you found in the Lord. But what of the rest? Why don't you demonstrate the new you? Volunteer to work with teens in your area, tell them about your checkered past, the grief it caused you, and how you found a better way. You can't change the past, but you could change the future for someone else.