The Catechism in Questions & Answers

198. How does the Holy Spirit show Himself as a divine person?

The Holy Spirit shows Himself as a person of the trinity of God by sending
human beings to spread the gospel, just as God, the Son. Acts 13: 4 relates: “So, being sent out by the Holy Spirit, they went down to Seleucia, and from there they sailed to Cyprus.”
He stands by those who profess the Lord when they are in distress: “Do not worry about how or what you should answer, or what you should say. For the Holy Spirit will teach you in that very hour what you ought to say” (Luke 12: 11, 12).
The Holy Spirit teaches the messengers of God: “But God has revealed them to us through His Spirit. For the Spirit searches all things, yes, the deep things of God” (1 Corinthians 2: 10).

Trinity: see Questions 51., 61. et seq.