"But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witness unto me both in Jerusalem, and in all Judea, and in Samaria, and unto the uttermost part of the earth"(Acts1:8).
As you are filled with the Holy Spirit, He dwells "upon you". He brings you into a new relationship with God and prepares you for service. The promise Jesus gave to His disciples to "receive power, after that the Holy Ghost is come upon you" had a specific purpose: "and ye shall be witnesses unto me both in Jerusalem, and in all Judea, and in Samaria, and unto the uttermost part of earth." The Holy Ghost came upon them to empower them as witnesses to the world.
On the day of Pentecost, as all the one hundred (120) disciples were gathered together in one accord in the Upper Room, suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and begin to speak with other tongues, as the Spirit gave them utterance" (Acts 2:2-4). Tongues of fire appeared as they were filled with the Holy Spirit on the day of Pentecost. This infilling of the Holy Spirit upon His followers prepared them for service, as it does for believers today.