If you have accidentally deleted the Settings icon from the home screen of your iOS device, don’t worry.
This tutorial will walk you through the restoration process, which works for iPhone, iPad, and iPod touch.
Restoring the iOS Settings Icon
Open Spotlight Search, and type Settings. Tap Settings.
Go to the Reset section > Reset Home Screen layout.
Your Settings icon should be restored, along with all of the app icons that were present on your home screen when you first purchased your device.