To add a Calendly Booking Calendar you can use this guide by Calendly to create your booking widget and generate your embed code.
Note: When selecting type of calendar embed note that you will need to select Inline.
Once the embed code has been generated make sure you have it ready to paste into the editor.
Select App Integrations
And then select Third-Party Integrations
From here click the Add a third party integration button and find Calendly in the popup that appears:
You should now see a field where you can enter the code from earlier:
After adding the code press back, this will take you back to your list of added integrations. Toggling the switch will enable the ability to add the calendar to your pages.
Navigate to the page you want to add the calendar, and click the add a section button. You will be able to see your widget under the category "Section Integrations".
Once you've added it to the page that you want the calendar to appear on click publish and it will now appear on your live site.