Hot corners allows you trigger specific actions on your Mac through simple mouse gestures. You can, for example, put your Mac to sleep, activate the Launchpad, or enable the Screensaver by moving the mouse cursor to a corner of your screen. This guide will teach you how to set up your hot corners.
How To Configure Your Hot Corners
Click on the Apple menu > System Preferences > Mission Control and click Hot Corners. A screen that reads, “Active Screen Corners” will be displayed. Hot corners can be configured by the means of drop down menus. You simply have to click on the drop down menu displayed next to desired hot corner and select the action you would like to occur.
Furthermore, if you would like to stop OSX from accidentally triggering hot corners, you can add a modifier key (or a combination of keys) to the activation of your hot corners. While selecting a default action for a hot corner, simply hold the desired modifier keys (Control, Option, Command, or Shift):
Repeat the operation for the other hot corners. When done, click on OK to apply your new settings.