Do these steps to install an app on your Oculus on development stages:
Step 1: Preparations:
1. Enable developer mode of Oculus Quest 2:
instructions provided from this link
2. Download & Setup SideQuest from this link
Step 2: Install APK via SideQuest:
1. Turn on Oculus Quest 2 and SideQuest on PC, connect them with USB cable. Following prompt should emerge in your Oculus Quest 2, make sure you allow USB debugging.
You should be able to see your device on top left corner of SideQuest. Click the button marked in red on the top toolbar of SideQuest will display all apps you installed on your device.
2. Locate the APK file you intend to download, click the button marked in blue on the toolbar.
Drag the APK file you have (for my case, it is called test.apk) to SideQuest. If following message shows up on SideQuest, then the installation is successful.
3. Two ways to Launch the App:
(a): through SideQuest. Return to the screen where presents all your apps. You should see the app just get installed. Click corresponding gear in the right column. Then you can manage your
app here.
(b): Through your device. Click button-apps on your bot tool bar, Expand ALL on the top right corner of the new prompted interface, then you should see an option called Unknown Source.
Click the desired app and you can see the app just get installed
Source: https://innovate.it.miami.edu/_assets/pdf/tutorial-for-installing-app.pdf