The Bible does not contain everything that Jesus Christ did or said, nor tell about everything of the other two persons of the Holy Trinity. St. John the Theologian wrote in his Gospel (John 21:25, NKJV):
25 And there are also many other things that Jesus did, which if they were written one by one, I suppose that even the world itself could not contain the books that would be written. Amen.
The Bible itself also says that we need guides, the Apostles, to the interpretation of God’s word.
Acts, chapter 8 (NKJV) reads:
26 Now an angel of the Lord spoke to Philip, saying, “Arise and go toward the south along the road which goes down from Jerusalem to Gaza.” This is desert. 27 So he arose and went. And behold, a man of Ethiopia, a eunuch of great authority under Candace the queen of the Ethiopians, who had charge of all her treasury, and had come to Jerusalem to worship, 28 was returning. And sitting in his chariot, he was reading Isaiah the prophet. 29 Then the Spirit said to Philip, “Go near and overtake this chariot.”
30 So Philip ran to him, and heard him reading the prophet Isaiah, and said, “Do you understand what you are reading?”
31 And he said, “How can I, unless someone guides me?” And he asked Philip to come up and sit with him.
That all said, be really careful whom you select as a guide to interpretation of Scripture, and even more so about those who claim they have new scriptures and more revelations from God.
“Beloved, do not believe every spirit, but test the spirits, whether they are of God; because many false prophets have gone out into the world.” (1 John 4:1, NKJV)
Acts Chapter 8... the Ethiopian Eunuch... Goes hand in hand with Romans 10:15-15. Philip was a missionary and was divinely appointed to be in the right place at the right time to witness/preach to the Eunuch. The Eunuch had been to Jerusalem, and had seen and been reading Isaiah. And along comes Philip, at just the right time, to witness to the Eunuch.
This is the roll of all believers - to share the word of God and the Gospel of Jesus Christ. Sometimes it might very well be with someone who has been investigating and searching (evidence that God has already been working on them through the Holy Spirit), and sometimes it will be with someone who has never read a single verse of the Bible.
But to stretch Acts 8 into a defense of the Catholic Apostolic tradition and succession... is misuse of God’s word and completely ignores the fact that God calls ALL believers into a form of priesthood. All believers are Ambassadors of Christ.
Christ Himself promised the Holy Spirit to us - as our guide.