Go to the top corner at the right of your screen near the battery indicator, there is an icon of the lock with a curved arrow click it, and disable it to get a rotation of the screen.
Most of the time iPhone users keep their screen in a vertical format.
When the Orientation icon is highlighted in white shade, the screen is locked into portrait mode.
The Control Center screen slightly varies in each iPhone model.
To control the Rotation Lock use a double-tap or triple-tap at the back of the iPhone.
So, the back tap is ready to use!!!!!!