How to embed an iframe in Confluence page?

1. Log in as your Confluence Admin, go to manage add-ons
2. Enable all the modules of the Confluence HTML Macros

3. Insert the Include HTML Macro when you are creating/editing a page.

   a) Go To Insert More Content > Other macros

   b) Search for HTML macro

   c) Paste the following code inside the macro

4. Save the page

     <iframe src="https://calendar.google.com/calendar/embed?src=3g3ie767f4ji0e72icgtfjg%40group.calendar.google.com&amp;c" noborder="0" width="830" 
     height="800" scrolling="yes" seamless></iframe>

 <iframe src="https://calendar.google.com/calendar/embed?src=3g3ie767f4ji0e72icgtfjg%40group.calendar.google.com&amp;c" noborder="0" width="830" 
 height="800" scrolling="yes" seamless></iframe>

When adding a macro I did the following:

1. "Other Macros"
2. Search for "iframe"
3. Select "Iframe" macro
4. Enter only the iframe url, and any other required settings.