I will wait until you have watched the video. That does not really explain where evil came from or what it is. It is very interesting and should humble us all in areas of mystery that we so often think the human mind can actually apprehend.
Okay, I've watched the full video now. It's well explained and clear, but I didn't really learn anything new.
Here's what I posted previously (to have it as a reference in this post), "I haven't watched the video yet, but I'd say that evil came from the devil taking his eyes off the Lord, and looking at himself and his attributes with pride, forgetting that everything he had was because God had given it to him.".
This was a very brief summary of my thinking and praying about this (mostly when I was very young in the faith, nearly 40 years ago).
Now, I'll give a slightly longer summary: I realised that evil is not something in itself, but only a corruption of something good. This means that the devil, whilst created very good, was given the ability to become corrupted (as Adam and Eve were).
How could this happen? Well, it's desire that leads to action; but, the devil would have started with very good desire; so, how could that reduce to the point that it became sinful?
Here's an analogy that I believe shows, roughly, how this could happen. Suppose that you are driving on a motorway with a minimum speed limit of 40 m.p.h.. You are driving at 70 m.p.h. and reduce the pressure on the accelerator a little. Your speed reduces to 60 m.p.h. (still no problem and no sin). You reduce the pressure a little more, then a little more, until, finally, your speed slows to 39 m.p.h., at which point you are committing "evil".
Every creature depends upon God for life and goodness, but, suppose we lessen our focus on him a little. We are not committing evil, just bearing a little less fruit (some thirty-fold, some sixty-fold and some an hundred-fold). We spend a little less time in the means of grace (hearing preaching, praying, reading the Bible, godly fellowship, etc.) and God gives us a little less of the grace that we need to produce good fruit. If this process continues, then we will enter into, not merely less good fruit, but some bad fruit (evil), to some extent at least.
I believe that something like this is how evil started, the devil focusing less and less on the Lord until he reached the point where less good fruit turned to bad fruit (looking to himself in pride).