ChimpChimp

Step 1: Download the file

Step 2: Download Mobile VR Station on your headset

Step 3: Open Mobile VR Station

Step 4: Go to Local Files > All Folders > Android > data > Scoped Storage Actions > "Step 1: Request Access"

Step 5: Click your device name in the top left corner of a pop up that should appear

Step 6: Go to "Download"

Step 7: Find the game file and click its expand button

After that, you are finished, you will find the game in the Unkown Sources Tab