In short
Christians would say: ask Him. God promises that those who seek Him honestly will find Him. Alongside the evidence of creation and conscience, the clearest proof is Jesus, and the surest way to know is to begin a relationship and see.Faith is not a leap into the dark but a step toward the light. Many who doubted began by praying an honest prayer: God, if You are real, show me. He is not afraid of your questions.
Read the Gospels, pray honestly, and consider walking with people who know Him. Knowing God is less like solving a proof and more like meeting a person.
What Scripture says
“And ye shall seek me, and find me, when ye shall search for me with all your heart.”
Jeremiah 29:13 (KJV)“Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you:”
Matthew 7:7 (KJV)Where to go from here
Still wondering? Ask Simon, a companion who points to Jesus, or bring it to God in prayer.