Hi,
To insert a completely new element, you would use F_ApiNewElement() or F_ApiNewElementInHierarchy(). For some reason, neither of these appear in the PDF bookmarks of the latest FDK reference, but they are described in the text.
You also say something about an "existing" element and "cloning", so I'm not exactly clear on what you want. To copy an existing element, you can select it and use F_ApiCopy() / F_ApiPaste.
One thing I would note, though, is that you are using words that are associated with objects in an object-oriented program. FrameMaker objects are not really the same... they are just things in the session that have properties. There is no real concept of "cloning" or "instantiation" with a FrameMaker object.
Russ