To save anything(imported geometries...) as a Prop, just save it to the Prop Library.  You will have made a Poser .PP2 file, in your current ?:PoserRuntimelibrariesprops directory.

When your asked to save as a Smart Prop, say yes, and the next time you use that Prop Library Preset; it will load into the scene, Parented, if you had it Parented(to M2's head} when you saved it to the library.