Write a letter to someone who you feel has done you wrong, explaining your perspective.  Then burn, throw away or recycle it as you verbally express your forgiveness.

Make a list of people you feel negative emotions towards.  Next to each name descibe why these feelings come up for you.  Envision a conversation with each person, where in the end you tell them that you have forgiven them.  Once you have completed the list, get rid of it.

Complete a forgiveness meditation series.  We like the Headspace app, but there are many others available online too.

Find a therapist to work with in person, or try out an eservice like Talkspace.

Make a list of all of the times you have done wrong by others.  Work through the list by accepting where you were at the time, offering a mental, written or verbal apology (this can stay private) and hug yourself as you tell yourself that you are forgiven.