I don't know how to use the SDK. I don't use it at all. I just need to know how to place an .mdl file into scenery.
That's what Felix is saying though. You *have* to use the bglcomp from the SDK (Software Development Kit) to do what you want to do with the Homeworld Carrier. One reason is that you have to write a small .xml file that contains the latitude, longitude, eltitude, heading..., and source model. The bglcomp compiles that into a bgl file that you place in your add-on scenery "scenery" file.
I'm not 100% positive, but I think you can download the needed utilities from the Utilitys DL pages. A search for "Scenery design" should give you enough options to find what you need.