Mycloud Ex2 Ultra access from Oculus Go VR Headset

I want to stream video files from a MyCloud Ex2 Ultra to a Oculus Go VR headset from a foreign WLAN. Therfore I want to use the MyCloud App on this Oculus Go headset with Android OS like I use it on my Android phone. But for this I have to sideload the WD .apk for the mycloud ex2 ultra, because the App can’t be installed directly on the headset by using Google Play Store like on a phone.
But which is the correct .apk package file for android systems?
Did somebody the same procedure and had success?