How to add extensions to Netscape 8?

I have a Firefox xpi that I wrote, that works fine in Firefox and Netscape 
8.  The problem is, that I don't know how to install the extension as part 
of my app's setup script.  For Firefox, it's just a matter of calling 
Firefox -add-global-extension (or whatever).  How is this done in Netscape?

Also, I have an extension that does the same thing, written for IE.  How do 
I add *this* to Netscape 8?  I can't find any documentation for any of this!

Thanks!