How can we embed simulations developed in another tool, such as Enable Now?

First off I recommend you take a look at Capture as I suspect that would be a welcome alternative to Enable Now.  However, sometimes it makes sense to embed projects from tools like that.  There are two main ways.

1. If the tool provides a hosted publishing option that can give you a URL or embed link (e.g., like Youtube). Then you can use the Insert -> Video and pick the Web Page Link option OR if embed code, use the video embed code.
2. If the tool enables you to publish it as a "web package" it will likely create a launcher page and/or assets.
   1. Navigate on your computer to the folder which contains the launcher page and all the folders/assets needed to run the package. 
   2. Select all items and Zip (compress) the contents.
   3. Under Engage in the ribbon tool bar - choose HTML Widgets (last choice on the right) and then upload your HTML widget.
   4. Add the HTML widget to your page.
      
      
      Additional Widget Info
      Knowledge Base Article on adding HTML Widgets
      Question on calling a function from an HTML widget