First you need to know why God deserves first place, and you will find that out by knowing who He is.
1-He is the all powerful all knowing creator of the universe. If God is powerful enough to create the universe, then there really is nothing impossible for Him.
2-He is not just all knowing and all powerful, but He is also Holy and He cannot sin.
3-He is also just. The day will come when He will judge every human being who didn't believe in His son according to their deeds.
4-He is also eternally loving. He loved the entire world so much that He gave Himself for all of Humanity when He was tortured, humiliated, and nailed at the cross.
So in a summary, the true living God who is the all powerful creator of the universe who is Holy and worthy of all obedience, praise, glory, and honor loves you with an everlasting love that is able to erase all your trespasses against Him. This love forgives your sin, but knowing who He is should want you to be more like He is. He hates sin because sin destroys, divides, goes against His nature and leads to death. He gave us all His commands in love because He knows what is best for us.
To put God first in your life you must confess your sins to God and understand they lead to death, repent from them, ask God to heal you, and follow Him.
God Bless you!