On the top-right corner, you should see a tiny settings gear. Press and hold that little icon for about five seconds to reveal the System UI Tuner. You will get a notification that says the hidden feature has been added to your settings once you let go of the gear icon.
How do I find the hidden menu on my Android?
Here’s how: Open the dialing pad as if you were making a phone call. Type *#0*# The menu will appear automatically.
What is hidden code?
USSD codes are hidden codes that allow you to access certain features of your mobile phone without the need of going through your settings. These feature codes look like a combination of numbers and symbols and normally begin with an asterisk (*) or a hashtag (#).