As Apple mentions in the Mac User Guide, you can also click on the Siri icon in the macOS menu bar to type a prompt, or you can ask Siri a question verbally and include the phrase "Ask ChatGPT" to tell Siri to forward the prompt.
Before you can use ChatGPT in Apple's apps you must first turn on Apple Intelligence, Siri, and the ChatGPT extension in the System Settings app (or the Settings app in iOS).
If you've also enabled Siri and the ChatGPT extension in Apple Intelligence system settings you can now use Siri itself to prompt ChatGPT for answers.
By enabling all the Apple Intelligence and ChatGPT Extension features above, you effectively turn Siri into a front end for ChatGPT - into which you can type prompts for it to answer.
How to use Siri to get answers from ChatGPT Using Siri to get answers from ChatGPT.
