1) Try to quit the application(s). 

You can do this by either 

  • At the top of the screen select the drop down under the name of the application



  • Right clicking on the application in the dock. Press down on the trackpad with two fingers



2) If that doesn't work then you can Force Quit the application(s)


Go to the apple at the top of the screen and choose "Force Quit"



From there you can select which application(s) you wish to close.