Siri on your Mac
You can talk to Siri on your Mac mini and use your voice for many tasks. For example, you can find files, schedule meetings, change preferences, get answers, send messages, place calls, and add items to your calendar. Siri can give you directions (“How do I get home from here?”), provide information (“How high is Mount Whitney?”), perform basic tasks (“Create a new grocery list”), and much more.
Important: Mac mini doesn’t have a built-in microphone, so you must connect an external microphone (sold separately) in order to use Siri. After attaching your microphone, select it in Sound preferences (click the System Preferences icon 
Note: To use Siri, your Mac mini must be connected to the internet and a microphone. Siri may not be available in all languages or in all areas, and features may vary by area.
Speak to Siri. Click Siri 
in the top right of a Siri result to pin it to the Today View. To see it later, click the Notification Center icon How to use Siri on your Mac.