The Old Testament is to be understood in a New Testament way, in the light of the Church. The Old Testament contains the preparation for the coming of Christ, promises, prophecies, as well as types
and antitypes of Christ. The events of the OT being the shadow and the events of the NT being the truth and fulfillment. Scripture must be explained and the Church interprets it. In
1 Timothy 3:15 we're told that the pillar and foundation of the truth is the Church.
Here are just a few other examples:
Adam and Christ
Eve and the Mother of God
Earthly paradise and Heavenly paradise
Sin through Woman and Salvation through the Virgin
Eating the fruit bringing death and partaking of the Holy Gifts bringing life
The forbidden tree and the saving Cross
The gold serpent on the pole and the saving Cross
The serpent/deceiver and Gabriel preaching good tidings
Woman told she will bring forth children in sorrow and the women at the tomb are told to Rejoice
Salvation from the flood in the ark and salvation in the Church
The three strangers with Abraham and the Holy Trinity
Jacob's ladder and the Mother of God (the ladder of the Son of God's descent to earth)
The sale of Joseph and Christ's betrayal
Slavery in Egypt and the spiritual slavery of man
Crossing the Red Sea and Holy Baptism
The burning/unconsumed bush and the perpetual virginity of the Theotokos
The Sabbath and the day of Resurrection
Circumcision and Baptism
Manna and the Lord's Supper
The Law of Moses and the Law of the Gospel
Sinai and the Sermon on the Mount
The tabernacle and the NT Church
The Ark of the Covenant and the Theotokos
The serpent on the staff and Christ nailed to the Cross
Aaron's rod and our rebirth in Christ
Isaac a rejected sacrifice vs. Christ (even told in OT there would be a lamb- but there was a ram instead- the lamb was Christ)
Moses' account of fall into sin vs. parable of the Prodigal Son
When speaking of certain verses- here's one: Pslams 137:9 says, "Happy [shall he be], that taketh and dasheth thy little ones against the stones." I totally agree with it. Little ones refers to our sins being dashed when we repent and turn to Christ. Everything in the Old Testament is a type or an anti-type of Christ. This is how the Church interprets that scripture. In the New Testament we have an example of the Ethiopian Eunuch reading Isaiah and claiming that he couldn't understand it unless it was explained to him. It's because there is a deeper meaning than the literal, when it comes to the scriptures.