There are four primary ways that God has made Himself known to His creation:
1) Through the
Incarnation, where Christ came to earth to reveal God's love in human flesh, to
spend time with humankind, to suffer and die for us on the cross, and to defeat
death with His resurrection.
2) Through the Holy
Spirit, who reveals Himself by living inside all who accept Christ as Lord and
Saviour.
3) Through the texts,
revelations and the miracles recorded in the Bible.
4) Through the testimonies, miracles and experiences of God at work in the lives of other Christians.
Atheists do not currently find those four ways convincing enough, otherwise they'd be believers. And that is fair enough - each one of those four ways usually requires lots of thought, investigation and experience, and I commend any unbeliever who is courageous and diligent enough to give Christianity the depth of exploration it merits.
But if you want to
know God, you have to take Him on His terms - and His terms are the four ways
above. If you won't have Him on those terms, then you're not engaging with the true nature of God's revelation, or evidence for His existence.
Further Reading: See my God Tab