if you downloaded the apk on quest then download the app Mobile vr station in the Meta store and Once downloaded go to local files then Android then data then Scroll down till you see Scoped storage actions then click "step:1 request access" then Something should pop up and at the top left select where it says your headset model (quest2/3 or whatever you're on) then go to the download tab and find your apk file and click the small white box at the top right corner and it should ask you if you want to download the game and click download and once it downloads then go to your app library and at the left find unknown sources and your app should be there (i hope this made sense 😭)
I had to upload it to Google drive, because this website only allows 3mb of file size