Why do you think it needs to show up in the CIW? There's no requirement that a PDK is "attached to the CIW" (whatever that means - I assume you mean there are some menus in the CIW).
All you should need to do is reference the PDK's libraries from your cds.lib - so you can just include their cds.lib in yours, and any code needed will be loaded from the library's libInit.il file. No need to put anything in your .cdsinit. Some of their PDKs come with some utilities, but I think these get installed the first time you reference the library.