Google's Gemini Assistant for Calendar is only available on the desktop version of the Google Calendar at present, with the Gemini icon next to ... or your computer goes offline.

Gemini is behind the ‘Add to Calendar’ button that interprets your emails and creates an event. Gemini is behind the ‘Add to Calendar’ button that interprets your emails and creates an event.

Once you're in, go to your Google Calendar and find the "Ask Gemini" icon in the top right corner. Click on that icon to see a list of suggested prompts and a space to enter your own prompt.