"The Hebrew said that the whole divinely inspired Scripture may be likened, because of its obscurity, to many locked rooms in our house. By each room is placed a key, but not the one that corresponds to it, so that the keys are scattered about the beside the rooms, none of them matching the room by which it is placed. It is a difficult task to find the keys and match them to the rooms that they can open. We therefore know the Scriptures that are obscure only by taking the points of departure for understanding them from another place because they have their interpretive principle scattered among them" (Joseph W. Trigg Philokalia 70-71).
Christ, of course, is the master key to all the rooms.
Such an explanation of understanding Scripture may be disheartening at first glance, but it should not be. We are not left on our own in the house with many rooms. We have guides, like Origen, like Cardinal Martini, like Luke Timothy Johnson, the recently deceased Eugene A. LaVerdiere, SSS, and the late Raymond Brown, SS. Closer to home there are those who preach the word, helping us not only to make sense of it, but to appropriate God's words. In a particular way the church is blessed with those who, in their preaching, undertake serious engagement with the readings in order to expound on them for the purpose of applying them to our life now. In order to do that one must have the confidence that Scripture is always relevant to our lives here and now and who, while they seek to make Scripture comprehensible, do not unduly reduce and/or oversimplify God's word, which results in nothing but clichés and pious platitudes.
On a personal level the practice of lectio divinia by which we seek what God tells us through the text is also indispensable. Like all things we desire to learn, in order to unlock the riches of Scripture we must apply ourselves, we must be teachable, which entails finding teachers and books, as well as being patient and persistent. Engagement with Scripture is perhaps the most immanent way that God remains with us and among us. As St. Jerome taught: "Ignorance of Scripture is ignorance of Christ."
There are two books I recommend to everyone who is unfamiliar with Scripture, but who want to engage the sacred texts more meaningfully:
From Genesis to Apocalypse: Introducing the Bible, by Roland J. Faley, TOR
And God Said What?: An Introduction to Biblical Literary Forms, by Margaret Nutting Ralph