The Accessibility Menu provides a large on-screen menu to control your device. You can control gestures, hardware buttons, navigation, and so on.
a) To use this feature, system navigation buttons should be enabled: go to “Settings”->“Button & gestures”->“System navigation”->“Buttons navigation”.
b) Then go to “Settings” -> “Accessibility” -> “Accessibility Menu” -> “Accessibility Menu shortcut”, touch the trigger to activate it->touch “Allow” -> “GOT IT” ->the accessibility button 
will appear on the screen.
Note: Available settings and menus may vary depending on device model and software version.
