Unless you have a MIDI controller, Alter/Ego is best used as a VST in a DAW. Standalone Alter/Ego can only be controlled with a MIDI controller as far as I know, so find the .dll and get the VST cersion in your DAW of choice.
From there, it is basically like an instrument in the DAW, so you can open a midi in the DAW and change the instrument to Alter/Ego.