Have you ever been asked by a non-Catholic Christian, “Where is that in the Bible?”
This question usually rests on the presupposition that the Bible is the sole rule of faith and practice for Christians. This view is also known by it’s Latin name, sola scriptura.
In the words of Protestant apologist, James White:
“The doctrine of sola scriptura, simply stated, is that the Scriptures and the
Scriptures alone are sufficient to function as the regula fide, the “rule of faith”
for the Church. All that one must believe to be a Christian is found in
Scripture and in no other source. That which is not found in Scripture is
not binding upon the Christian conscience.” 
This raises an interesting question, how do we know what books belong in the bible, let’s start by taking a look at the new testament.
Sometimes people seem to assume that the New Testament fell from heaven, complete, and with no questions of what belongs in it, but actually the Church had to decide which books were inspired and which were not.
In the second and third centuries, many “gospels” were falsely attributed to the apostles; such as The Gospel of Thomas, and Peter, and James etc.
Other revelations and epistles may not have been falsely attributed, such as The Epistle of Barnabas, The Shepherd of Hermas, and the Didache but were not deemed by the Church to be Scripture.
The first time we have a magisterial document that recognizes in full the canon of Scripture was at the council of Rome in 382 under pope Damasus I (soon reiterated by the councils of Hippo and Carthage). The list of books given by the council of Rome is the same lists Catholics use today. 
Regarding the New Testament, the council declared:
Likewise, the list of the Scriptures of the New and Eternal Testament, which the holy and Catholic Church receives:
of the Gospels, one book according to Matthew, one book according to Mark, one book according to Luke, one book according to John.
The Epistles of the Apostle Paul, fourteen in number: one to the Romans, two to the Corinthians, one to the Ephesians, two to the Thessalonians, one to the Galatians, one to the Philippians, one to the Colossians, two to Timothy, one to Titus, one to Philemon, one to the Hebrews.
Likewise, one book of the Apocalypse of John. And the Acts of the Apostles, one book.
Likewise, the canonical Epistles, seven in number: of the Apostle Peter, two Epistles; of the Apostle James, one Epistle; of the Apostle John, one Epistle; of the other John, a Presbyter, two Epistles; of the Apostle Jude the Zealot, one Epistle.
Thus concludes the canon of the New Testament.
So here’s a question: If you are willing to accept the inspiration of the New Testament, are you not also required to accept the authority of the Church to tell us what belongs in it?
On the other hand, if one is not willing to accept the authority of that Church, are you able to know with certainty that the New Testament documents are inspired?
 Some books in the Damasine list appear unfamiliar when compared with modern Bibles as some books were later combined or titled differently