This video explains how to use the Speech Recognition tool on the Mac, which allows you to speak most of the commands that you use on the computer. To enable speech recognition, go the Apple menu, select System Preferences and click on Speech. Then click on ‚ÄúOn‚Äù next to Speakable Items, and click OK.
Then you can choose your microphone, and adjust the volume by clicking on Calibrate. Under that you will see the Listening Key, which is the Escape key on the keyboard. You can change the listening method by clicking on Change Key. Here it gives you the option to listen only when the key is pressed, or set up a keyword to say before you give a command. Then check the box next to Upon Recognition and choose a sound that you will hear as an acknowledgement. When speech recognition is turned on you will see the control on the desktop, which you can move anywhere you want it.
To use Speech Recognition, press and hold the Escape key on the keyboard while you speak your command to enable voiceover.