I usually will explain the term with a larger discussion on the Creed itself.
I explain the origins of the Creed and why it was written. I explain in simple terms that it was responding to a priest named Arias who said the Jesus was like a great angel but not God.
I then say that the word “consubstantial” is used because it means “of the same substance”. Meaning if God the Father is God, and Jesus comes from God, then Jesus is just as much God as the Father is God.
There’s usually more context leading up to that point because of the line “God from God, light from light” which most people have no clue what it means. I then have them think of a dark room, will any light ever spontaneously and without reason burst forth in the room? Or will a lighted room suddenly go dark for no reason at all?
No, because darkness begets darkness, and light can only come from light. Just as a dog will never give birth to a cat (usually get a good laugh there).
Likewise, Jesus is God because He is begotten of the Father, who is God. Only God comes from God. Therefore Jesus is of the substance of the Father. Thus we say “consubstantial”.