You do not have to prove the Bible - just use it. Use it even with people who say they do not believe it. God has promised to honor His Word. If you expect God to use you, talk about the Savior - and always encourage those with whom you share to invite Him into their lives. As you talk to people about the Savior, you will discover that many are ready to receive Him the very first time you talk to them.
Size is approx.
As a young boy I used to visit my uncle's peach orchard. We would always pick the ripe peaches, but leave the green ones. Two days later, we would return to the same tree and pick more ripe peaches. Every two days we would pick yet more ripe ones. So it is in our witness for Christ.