this guy making it...

https://www.youtube.com/watch?v=Fq0-dAC5lZE

Claye Hayes does a lot Bowyering.  He has some good tips. I live in the land of Western Red Cedar, if the Eastern is anything like the western variety its to soft and weak.  But then again you can build a bow from almost any wood.

Eastern Red Cedar is actually a Juniper not a cedar. Western red cedar to too soft and brittle for bows!

Eastern Red cedar will make a good bow but I'd back it with rawhide, silk or linen. You can make a good bow with just sapwood ERC. I've seen and shot one and was amazed.
You might be able to make a good bow with western red cedar but I've never done it. I know you can make arrows from it.