After you have loaded the plugin and the xml files into their proper folders, when you start Mach3, it will ask you if you want to run the dspmc, pport, or other motion control device. If this message doesn't display at startup, under the function cfg's tab in Mach3 it has a selection that says reset device selection and you will be able to chose which device you want to use the next time you start Mach3.
Mike