It can be difficult to understand how the end of the Bible's storyline interacts with and informs its beginning and middle. Referring to this reality, theologians tend to talk in terms of the already and the not yet.
It is important that we seek to understand this theme of already and not yet. That is to say, the promises God made to his people—all the way back in the Garden of Eden, to Abraham, to Israel, to David, and throughout the centuries—are beginning to be fulfilled through Jesus the Savior. God’s end-time promises are already being fulfilled through Jesus. One way we can put it is that we live in an age of eschatological fulfillment. Eschatology has to do with the last things.
At the same time, we need to understand that while God's promises are being fulfilled in and through Jesus, they are not yet complete. There's more to come.
So understanding the end and how the end has been brought into the present helps situate us in the story of the Bible, and helps us understand where we sit in the unfolding message of the Bible. And it orients the way we should think about God's promises as already begun to be fulfilled, but not yet fulfilled in their completeness. And it helps us have confidence that God has worked, God is working, and God will work.
In the end, this should frame the way we think about our place in the overall story of the Bible.