God isn't a created being. He is infinite, and creation would suggest a finite nature.
i don't know what grade level. the child is. If, say, a bright 4th or 5th grader, maybe younger, this may all make sense...
You could start with telling the child that no scientist can really tell us where the universe and its rules, like gravity, or even time, came from. We know of them in the NATURAL realm. What is not of the natural realm is SUPERNATURAL. It seems the natural realm has a supernatural cause since we can find no natural cause for it.
Now, in the natural realm things have a beginning and an end. That is not at all necessarily so in the supernatural realm. It is endless. It has different rules, rules we have a hard time even imagining. Ask the child to think of how hard it would be for someone raised on a remote, primitive island, to imagine computers, highways, smart phones. It is much harder for us, who live on this remote little planet of earth, to comprehend what we presently cannot see in the eternal, everlasting, realm.
Also, ask, "Can something come from nothing?" When you get "No" say, "Well, if there is something, that means there
always had to be something or Someone, because nothing can't make anything. Also ask if a mindless "something" could make rules and show intelligence, design and order such as we see in science and all around us.
Even in this realm we see that can't happen. Therefore we can conclude that the design and order we see around us has an intelligent cause. That Intelligent Cause, that has always existed, is what people call the Creator.