If you want to display a map created at Google.com you can still use the little globe tool for publishing the map on the page. But if you'd like to use one of the RTA Custom Maps you've created on either Map Wizard or Map Center, there are a couple of steps... (But once you've done it once, it will be easy)
1. It has to be a saved map, so locate your saved map ("My Maps") by clicking on the link and opening it and click on "View and Share Saved Map"
2. Adjust the display of the map on the page: zoom in or out Until you get it the way you want it.
3. Copy the link at the bottom of the map
4. Go the page you want the map display to appear on. Put your cursor where you want the map to be.
5. See that little button that reads "RTA Map"? Click it it will put some RTAMap tag codes on your post page. (Do not click on the "Globe" that is for Google Maps only -- not the RTA Custom Maps).
............5.a. If you're editing a post and putting in a map, in order to see that RTA Maps link, you need to click on "Go Advanced"
6. Paste the link between those two tags, (one more step)
7. Edit the link: Replace the word custom with display
8. Click save
And it shows up!