Yet the Book of Enoch is not part of the Bible. Like with the Koran, we have no need of it to understand one of God's holy days. Leviticus 16 was written long before all these traditions developed, which means we need to start there, not with the ideas of carnal men that came a millennium later, or two millennia, in the case of the Koran.
In Titus 1:14, Paul specifically warns against giving heed to Jewish myths and fables, and the apocryphal Jewish works that the Correspondence Course uses as proof certainly fit that description and warning. II Timothy 3:16 says that Scripture is profitable for doctrine. Extra-biblical fantasy is not. Mythical stories have no validity as a starting point for understanding what God teaches about the Day of Atonement.