After embedding the calendar on my website, how can I enable viewers to subscribe to my calendar?
You can enable viewers to subscribe to your embedded calendar by adding a HTML code in your webpage. You can get the HTML code in Settings > Calendar > My Calendar > Sharing and permissions > Link to option. By adding this HTML code to your webpage, your calendar will be embedded as a button on the website, which the viewers can click on it and they will be subscribed to your calendar.
Refer here to know more about sharing Calendars.