You can follow the Instruction provided by Google here:
https://support.google.com/maps/answer/3544418?hl=en
  1. Navigate to Google Maps
  2. Click the hamburger icon (3 vertical lines) on the left
  3. Click the Share or Embed Map option
  4. Select the embed option and take just the https...portion for example https://www.google.com/maps/embed?pb=!1m14!1m12!1m3!1d1563190.4465308965!2d-74.72432305!3d40.07304!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!5e0!3m2!1sen!2sus!4v1450392106406

Then in onMessage navigate to the Page you were trying to place this on and place the URL in the URL portion of a Iframe.

To add a Iframe to a Page navigate to:
  1. onMessage
  2. Website
  3. Site Name
  4. Click Edit Page Content from the editing wrench of a existing Page, or Create a New Page
  5. Drag the Iframe content type from the left hand side onto the area of the Page you are looking to display this on
  6. Enter the URL of the Google Form for View Form
  7. Enter a Height of 1000 (you can adjust this number if its too large or too small as needed) 
  8. Click Save