First, ask forgiveness from God. If you're a Catholic able to receive confession. Go and confess your sins.
Next, ask God for the strength and wisdom to speak to those persons you've offended and ask they're forgiveness. Go and do this. Do so in love and without the expectation of nothing more than your expression of love to them.
You can flip this around, as the opportunity to ask an individual for their forgiveness may present itself quickly and in the moment but always start with prayer to God. Go to Him first for all.
As a Catholic confession is the sacramental norm but that never prevents one from asking for forgiveness as only God knows your heart and its true state of contrition.