To get a map on your web page, you just add 2 simple lines. With this Designer you can create and preview a simple map and get the matching Plug and Play Maps <script> to copy and paste into your web page (you get the other <script> from Google). First, enter the web address (http://...) of the data file you want to map; next, you will see a live map preview that you can update with other settings for how you want the map and data to look.
You are designing the map and matching Plug and Play Maps <script> to copy/paste into your web page. This design tool only lets you create a map with one data file; see the gallery and How To pages for examples and information on having more than one map layer.