The first Biblical reference to free will is in Genesis 2:17. "But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die." It does not say, "you will not eat of it" or "you cannot eat of it," as in a programmed robot, but "you shall not eat of it," as in "you have a choice, and here are the consequences."
Of course, if the Bible carries no weight with you, then you still have evidence of free will in and around you. Did you feel forced to ask your question about freewill? Could you have changed your mind and not bothered to ask it?
To me, the mess that this world is in is ample evidence of what happens when free will is exercised in the wrong direction. The horrific things are evidence of free will. We can't blame God for the decisions we make. Of course, the alternative, I guess, would be to wish that God had created us all as robots. Would you have preferred to be a robot?