The Holy Spirit is God. The Father (generally called God), the Son (Jesus Christ), and the Holy Spirit are one God, but are not one another. These articles are based in what the Bible teaches about Him.
It's clear from simply reading the New Testament that baptism by the Holy Spirit is not just for the apostles (Jesus' first disciples). To see this, we only need to go to the most famous verse in the whole Bible, and read it in context. It is, of course, John 3:16. It's important to read the whole section in John 3.