What's up Llnikki! If you can pick out the melody, then half the battle is over. The melody of the song is usually designed in the scale of whatever key the song is in. In finding the key, you're now able to pick up the song in chords. Being that about 98% of songs written are dominantly based on the 1, 4, & 5 of the scale, you can use those chords to find where the song is going. (For me, 4 if the vocalist goes up and 5 if they go down) Anything beyond the 1, 4, and 5 is used at the writer's discretion. Here, you can use the chords that you already know to find what they used. A good way to do that is to close your eyes and find the notes using your head and fingers. This is just a start of how I did it but I hope this helps. Be blessed!
~DB
That no flesh should glory in his presence. But of him are ye in Christ Jesus, who of God is made unto us wisdom, and righteousness, and sanctification, and redemption: That, according as it is written, He that glorieth, let him glory in the Lord. 1 Cor 1:29-31