Descartes argued that he had an idea of God as a perfect being. His idea of God is an idea of a being who is perfectly good, perfectly wise, and so on. In fact, he argued that the idea itself is a perfect idea, and therefore it could not have come from anywhere except from a perfect being. That is, the idea of God must have come from God. If this argument works, it gets us from knowledge of our own mind to knowledge of something outside us and much greater than us. It gets us to God.
