"'Indeed, all the prophets from Samuel on, as many as have spoken, have foretold these days. And you are heirs of the prophets and of the covenant God made with your fathers. He said to Abraham, 'Through your offspring all peoples on earth will be blessed.'" NIV translation
Peter continues on with the crowd by saying that not only Moses but all of the prophets were talking about Jesus. Then, he reminds them of the covenant that God made with Abraham in Genesis and that this promise had come true. That promise was for us as well because it says that "all peoples" will be blessed and that includes us. Isn't it awesome that, in the very beginning, God knew us and wanted us to be heirs and his children?
"When God raised up his servant, he sent him first to you to bless you by turning each of you from your wicked ways." NIV translation
Peter is reminding the crowd that God sent Jesus to them first. Do you feel blessed to have turned from your evil ways? Peter is trying to tell them that it truly is a blessing to turn from your sins. Many times, we may forget that it is a blessing to be freed from our old ways but when we stop and remember that our old evil ways take us further and further away from God then we can see the blessing of being turned.