Is Your screen wide that you can use a single hand to use or you holding something in your hand and you want to type here is a tip on how to use it
Go to settings
Locate gesture and smart location
Toggle the One-handed mode to "On"
Close the settings, comback to your home page
Whenever you want to have a smaller screen on the left or right side, swipe finger from home button to menu button in the bottom let start with left
LEFTHAND SIDE
It will look like this
RIGHT SIDE
It will look like this
TO EXIT ONE HAND MODE CLICK ON ANY EMPTY SPACE IN YOUR SCREEN