An iFrame can be placed in any WYSIWYG text area editor.

1. Edit the text area
2. Open to the HTML
3. Paste in the following code snippet: 

<IFRAME title="This is the title" style="width: 100%; height: 800px; margin: 0; outline: none" src="http://www.INSERT3RDPARTYURLHERE.com" >Your browser does not support inline frames.<br /><br /> Please visit <a href="https://training.weknowgovernment.com/?splash=http%3a%2f%2fwww.INSERT3RDPARTYURLHERE.com&____isexternal=true" target="_blank"> http://www.INSERT3RDPARTYURLHERE.com </a></IFRAME>

4. Replace the BOLD and UNDERLINED portions of the code with the URL you want to iFrame
5. Save text area

https://www.google.com/maps/d/embed?mid=1W4UqGuljXnnbudlF9KFzTekyw44