The Spirit of God has been around from the beginning. In the beginning before there was light the Spirit of God was above the waters. When God's son came to earth He died and came back to life. Before he died He told people that after He died and rose again from the dead He would leave and go back to be with His Father. But He would send us help in the form of His Spirit. I assure you that it is alive and well and will always be. After Jesus ascended back to be with God, one of Jesus's apostles, Peter, was teaching the people that were responsible for his death. As he was speaking he elaborated on words of prophecy from the book of Joel, after impressing upon them that they killed the very person that they had been foretold would be the Savior of mankind, they were moved to ask what they could do to fix their wrongdoing.
Peter told them that they should obey one of the commands Jesus gave just before he ascended back to heaven. This command was to be baptized in the name of the Father, Son and The Holy Spirit. He told them that if they did this they would have their wrongs, which is to say their sins, forgiven and when that happened they would also receive the gift of the Holy Spirit. If you realize that you have done wrongs in your life and I assure you, we all have and do, there is a way to remove the wrong in your life and make it right. God does not give us impossible tasks as some will say.
When we think about the Spirit of God, it is important to remember a conversation Jesus had when speaking to the Rabbi, Nicodemus. He told him that no one would enter the Kingdom of God if they were not born of the water and the Spirit. He also told him that the wind blows where it wills and you do not know where it will come from or where it will go and that is how people are born of the Spirit. I encourage you to meditate and pray about the Spirit of God and ask Him to help you understand and give you the wisdom to let it work in you and through your life. God will always help you with what you need and we undoubtedly need His Spirit greatly. Much more can be said but I will step back and let you pray to God about gaining understanding, knowledge and wisdom that can only come from Him and spiritually growing from reading, hearing, meditating and living out His word. May the Lord help you do just that. No one can help you understand this more than Him.