How to use EDITOR?

[user]

This question has probalby been asked a lot, but I just can�t get the 
editor to work.
I put the EDITOR tag in my XUL file, and it only shows a white box.But I 
cant load
something into the editor using the SRC attribute.All other XUL objects 
work (like button etc.).
The documentation doesn�t really show how to use the EDITOR.Can someone 
help me with this?