The Dock on a Macintosh desktop screen is stationary by default but can be configured to be hidden or minimised based on your preferences. Although hiding the dock is useful to maximise screen space, it can be cumbersome if you need to toggle between open applications on the Dock. As with other system settings, the Dock preferences are located in System Preferences and can be changed as frequently as you prefer.
Click the "Apple" icon at the top of the desktop screen. Click on the "System Preferences" tab on the pull-down list.
Click on the "Dock" icon in the System Preferences window. Drag the tab on the "Size" bar to the right until the Dock appears at your preferred size.
Click the checked box next to "Automatically hide and show the Dock."
Click the red button in the upper-left corner of the Dock window to save the changes and exit the System Preferences window.
Click the "Apple" icon at the top of the desktop screen, move your cursor to "Dock" and click "Turn Hiding Off."