The most straight forward approach on a Rift is to get the game code from Frontier store to load a copy in Oculus home and launch it there. That's how it worked for me, i had a plain ED install at first too.
ED is not running on the latest SDK of Oculus, probably a rather old one. Might be sth that needs to get installed via the store download, or manually by selecting/installing the right Oculus SDK. My best bet would be V1.4.