How to Open Activity Monitor
The Activity Monitor application, which is an included utility of the Mac OS X operating system, provides information and statistics concerning your computer's performance. The program is located in the Utilities folder of your Mac and can be opened by users with either standard or administrative accounts.
Open a new Finder window by clicking on the Finder icon in the Dock.
Click "Applications" in the Finder window to view the contents of the Applications folder.
Double-click the "Utilities" folder in the Applications window.
Double-click on the "Activity Monitor" icon to launch the utility program.
Click on the tabs at the top of the Activity Monitor window to view different information and statistics concerning your computer's performance.