How to use overlays?

Hello everyone.

I'm trying to generate a TPortal only visible to the user using the  
local machine, linking to an Island althow just localy avalible. To  
accomplish that I tryed to use an overlay containing the discribed  
TPortal, but I'm having some toubled setting up an Overlay.

Knows anybody a place to find an example about using overlays?

Thanks for any help.

	Waldemar