How do you forgive someone who traumatized you?

Im someone who believes that people can change for the better. And the person I'm talking about did. But if someone gave you trauma that is deeply affecting you in everyday of your life, how do you forgive them? My trauma isn't entirely their fault, but they contributed to it a lot, and I believe that a part of the healing journey is to let go of this resentment that I have towards that person. But it's so difficult. I love this person, and they didn't put me through it with malicious intent, they just didn't know any better. I want to forgive them and let this underlying resentment go so badly. Any advice on how I can do that?