Aquinas' Argument for the Uniformity of a Needed Being

"There's one necessary being that gives existence to all contingent beings," he says. "We can think of this necessary being as a kind of, what, a fountain? An ontological fountain, okay?" Aquinas is saying let's assume for the sake of the argument that time is everlasting,. Still everything in here, including time itself, is a contingent being because by definition it's the order of contingent beings.