If G‑d creates the world by simply desiring that it should be, and evil is that which he does not desire, then how is it that evil ever came into existence?

It’s a question based on an assumption: that G‑d despises evil because it is evil, because it opposes Him.

But evil only opposes G‑d because He chose it should do so.

He chose that there should be good and there should be bad. He chose that choosing goodness will provide connection, which is life, and choosing the bad will cause disconnect, which is death.

It is a raw, primal choice of His essence and being alone. And so within that choice all of Him is found.

And it is a choice that plays out in our world through the free choice of a human being, we creatures within whom G‑d breathed His very essence and being.

Behold, I have placed before you today that which is life and good, and that which is death and evil…choose life. (Deut. 30:15)

So that when you choose good over its opposite in this world, you connect to the G‑d point inside you.

You choose Him and He chooses you. You come alive with His life.

Choose life.

Likutei Sichot vol. 4, p. 1339.