In order to use your Quest in Developer Mode (which is required for sideloading), you’ll need to register as a developer organization
Visit this page and make sure you’re logged into the same Oculus account that your Quest is registered to. Enter a new organization name and tick the ‘I understand’ box to agree to the Oculus Terms of Service.
Open the Oculus app on your phone and make sure your Quest is turned on.
Tap ‘Settings’ in the bottom right
Locate your Oculus Quest listed in the Settings tab, and make sure it reads ‘Connected'
Tap on the arrow button next to your device, to reveal more options
Tap the ‘More Settings’ button
Tap on ‘Developer Mode’
Flick the switch to On instead of Off
Fully reboot your Quest – hold down the power button on the side and select ‘Power Off’ or ‘Restart’. You Quest should fully reboot in order to properly start in Developer Mode
After rebooting, your Quest should be in Developer Mode