Did you plan to work with the wav file of the vocal solo as a way of preparing for a live performance where you might be adding harmonies to the vocal solo? Or did you just want to add harmonies to this already recorded file?
If you don't intend to ever do this in live performance it might be quicker and easier to use the pitch shifter in Logic rather than running the recording through the H9. Logic's standard pitch shifter really is pretty good, and if you didn't want the specific sound of one of the H9's pitch shifters, you might be perfectly happy with the result of just using Logic's pitch shifter.
But in any case to send audio to the H9, if you have a multi-channel audio interface, if you open the I/O utility plugin, you can send audio to external hardware and receive it back from the hardware on any channel you choose.