The biblical writers do not spend much time trying to prove the existence of God. The reason for this is that God's existence is self-evident. In other words, it is obvious to all (even those who deny it). However, this does not mean that there is no evidence for the existence of God. Paul makes this clear in Romans chapter 1:
Romans 1:18-20, "For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse." (ESV)
Paul tells us several important things related to God's existence:
1. What can be known about God is plain to man.
2. God has shown what is plain about Him to man.
3. God's invisible attributes have been clearly perceived (understood) by man.
4. The evidence for these attributes is the things God has made (God's creation).
5. Man is without excuse if He does not believe in God. God's wrath is upon unbelieving man.
Atheism claims that God does not exist. God, however, has made it clear to all human beings that He does exist.
God's existence is self-evident. Those who deny this are suppressing the truth.