Acts 1:8 NKJV
“But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth.”
Acts 2:40-47 NKJV
“And with many other words he testified and exhorted them, saying, ‘Be saved from this perverse generation.’ Then those who gladly received his word were baptized; and that day about three thousand souls were added to them. And they continued steadfastly in the apostles’ doctrine and fellowship, in the breaking of bread and in prayers. Then fear came upon every soul, and many wonders and signs were done through the apostles. Now all who believed were together, and had all things in common, and sold their possessions and goods, and divided them among all, as anyone had need. So continuing daily with one accord in the temple, and breaking bread from house to house, they ate their food with gladness and simplicity of heart, praising God and having favor with all the people. And the Lord added to the church daily those who were being saved.”
After Peter was filled with the Holy Spirit he was filled (endowed) with power. He boldly told the people that they needed to be saved from sin. He said to them, “Be saved from this perverse generation.” In order for a person to be saved (become a believer) they must first come to a realization that they personally have sinned against God. They must then be sorry and ask for forgiveness, and turn away from their sins. They can not try to hold on to God and the world at the same time. The Holy Spirit enabled Peter to speak the truth to the people, and the Holy Spirit softened the hearts of the people to accept the truth. After the people received salvation they were baptized. They then followed the first believers in the Apostles’ doctrine, in fellowship, in the breaking of bread, and in prayer.