After installing, just right-click and hover on "Simply Fill with SimpleFill" and click on "Options". Add your information there which you want to appear in the Context Menu(Right-click Menu) and start filling forms in clicks.
Having added your information, right-click on input fields or drop-downs and click on the respective information you want to fill under "Simply fill with SimpleFill" context menu.
You need only two mouse-clicks per field to fill up any form. No matter how lengthy your Name or Address may be, just 2-clicks and you are done.
It works on Opera 15+
Visit http://plugins.compzets.com/simplefill to know more.