There are so many incoherent ideas-about and explanations-of Free Will, and yet its reality is so vitally important, that this is something that almost everybody needs to sort-out for themselves (assuming that they cannot ignore the explanations).
For Christians, Free Will is at the heart of the religion; and indeed, when (as has quite often happened) Christians neglect the matter of Free Will then the whole nature and practice of the religion gravitates into something quite un-Christian.
Indeed, when Free Will is taken out of Christianity, we get something approximating to Islam - in which obedience to God's will becomes the central virtue.
Nonetheless, taking Free Will seriously (as I think we must) takes us to places a long way from mainstream Christianity
1. Free Will is about thinking, not about actions. (Necessary to avoid incoherence.) Free Will is not all of thinking, not even most of thinking: Free Will is one kind, and the most fundamental kind, of thinking.
2. Free Will needs to be considered an uncaused cause - that is, the thinking of Free Will cannot be explained in terms of being a consequence of anything else. So we should not try to do so.
3. This means that the thinking of Free Will can be observed only after it has emerged. We cannot, and never could, perceive what is going-on in Free Will: Free Will emerges from a black box. We might observe it as it emerges from the black box, but could never see it being formed.
4. And when I say 'we' could not perceive or observe the workings or causes of Free Will - I also mean our-real-selves cannot do this. The (obvious) reason being that Free Will emerges-from our real-selves. So we-our-selves are in the position of observing thoughts as they emerge from our-selves - we can do so only after they have separated from ourselves.
5. What applies to our-selves also applies to God. God cannot, does not, perceive and know what is going-on where the thinking of Free Will comes-from. God cannot see-into our real selves; cannot analyse of Free Will: nothing can.
6. The 'workings' of Free Will are opaque, even to the creator - the reason is that God did not create that-which from-which Free Will emerges. That entity from-which Free Will (our real-selves) emerges is prior to creation.
7. God's creation works-around this; but Free Will is not a regrettable constraint. Creation is about bringing the Free Will of personal agents into voluntary, loving harmony and further creativity.
Note: What I have done above to is make a metaphysical assumption that Free Will is really-real and really-free (because implied and entailed by Christianity); and to reason from that assumption.