Website builder already has a calendar feature, but if you prefer your Google Calendar, it's possible to embed it on your website.

Start with this Google’s guide and once you see Embed Code (it should be like <iframe src="https://calendar.google.com/calendar/htmlembed…), copy it to the clipboard (ctrl+c or cmd+c on Mac) and go back to your website.

Start from the Left Toolbar > CONTENTS > Apps section, find Custom HTML Code on the list, and click it. Now you're asked for the custom code you want to enter, so just paste (ctrl+v or cmd+v) the HTML embed code you have copied from Google, once the code is there, just confirm with the "Continue" button. Now your calendar should be part of this subpage.