SOURCE:
Here are steps on how you can modify the settings for your “Super Users” account to have access to add iFrame code into articles:
1. Log in to your Joomla Administrator panel
2. Click on ‘Content’,'Article Manager’, and click on the button ‘Options‘
3. Click on the ‘Text Filters‘ tab.
4. Go to the ‘Super Users’ and select from the dropdown – ‘No Filtering’.
5. Save the options and refresh your site.
