Mateen Charbonneau, Sheikh Mateen Joshua Charbonneau achieved a certificate from Harvard University in Islamic Studies. He undertook Howza classes under esteemed scholars since 2013 and has been teaching at Imam Mahdi... Answered 3 years ago

The first step is to seek Allah’s forgiveness. Then one should make a determination not to do that action again. 

If the sin is between him and people depending on the situation he may need to settle that with the person also as if he took some property from another for example. 

Some sins require some extra actions such as kaffara like in the case of breaking ones obligatory fasting intentionaly for example.