Before Jesus went to heaven he told his apostles that they would receive the power of the holy spirit and they would all be his beholder to the world.
Then the apostles went into a room and started praying.
Suddenly a howling wind filled the whole room and a fire appeared on top of each of there heads and they were filled with holy spirit.
The holy spirit caused them to speak in different languages and the foreign people gathered around them because each the apostle was speaking to each of them in there foreign language. Some of the people thought the apostles were drunk but they refused.
After the refusal of being drunk Peter talked about Jesus's plan on salvation. The foreign people were very driven and were questioning what to do? Peter told them to apologize and get baptized for Jesus to forgive you.
That day over 3000 people were baptized and started trailing behind Jesus.