The early church organically adopted the Hebrew scriptures (what we now call the Old Testament), complete with the "Deuterocanonical" boos (what some call the OT Apocrypha). The had those scriptures all along. There is at least one early book (which I just heard of, and don't recall the name) by a Church Father that made the case for Christ and Christianity entirely from the Old Testament. St. Paul, if we read him carefully, was converted by the word of Jesus and confirming it by three years of study of the Old Testament.
The books that comprise the New Testament were all written before the end of the 1st century AD. They were known, read, protected, and taught from the entire time. Until the writings, Christians lived by the oral tradition (which Paul wrote of -- keep the word I taught you, etc.). Christian teaching was thus both oral tradition (the tradition of keeping these books and what they meant) and written tradition. It became important eventually to sort out the apostolic books from those with other origins, and so the list of books we have today was created and adopted.