I like to make peace with the past. I've done this in many ways. Once many decades ago, I wrote a love letter to a past love--I simply expressed my strong feelings and my understanding of why our relationship ended. My letter was met with a very loving response--that surely made pace with the past.
In another situation, I simply reached out to make amends, acknowledge the pain, and send good wishes going forward. I don't want to move on in life with open wounds, conflict, and pain--I want to do what I can to make peace in honest, positive ways with the past.
Sometimes my attempt to make peace, talk it out, and come to resolution are not met with a similar response. I remember a situation years ago where there was great conflict, I owned my part, apologized, and invited others involved to make amends, but those people were not interested in doing that. I had to put the issue to rest. I was at peace because I tried and did what I could. There was no more I could do.
Of course, better than making peace with the past, is to move ahead with as much peace and positivity as possible--to do what is right and good by others as much as possible. Like many, that's my aim.