Clark’s comment, written from a Reformed perspective, is a concise way of explaining the whys and wherefores of the Bible — the New Testament, in particular — to enquirers. You might also find it helpful (emphases mine below):
… We interpret the Bible with the church. So, we’re not just making up things as we go along. The Scripture is normative but it has to be read and it has been read (interpreted) with the church and we’ve consolidated that interpretation with the church in the confessions.
Can we have absolute, ontological certainty that we’ve gotten everything right? No, but great consensus on creation, humanity, fall, Christ, Trinity, and salvation is very comforting.
Rome didn’t make the canon. The early church gradually received and recognized the 27 books that compose the NT as having intrinsic marks of canonicity. In that sense the canon is self-attesting. The church did not make the canon in some committee room. The church, over time, in various places, but quite early and rather unanimously (with a few minor exceptions) received most of the NT quite early (by the middle of the 2nd century).