What headset do you have? Is it a Quest headset?
.apk files are android files, or standalone Quest files. You'll need to create a Meta Developer account and use Meta Quest Link and Meta Quest Developer Hub to upload .apk files to your Quest Headset. You can also use https://sidequestvr.com/ to install them on your headset (which is slightly easier than going through the hassle of creating a meta account). But again, they are for Quest only.