Ah yes, I didn't realize you were on a mac.
I personally haven't used IAC on my mac, but I imagine it's not much different than using other virtual midi port software.
Maybe this walkthrough will help you?http://www.johanlooijenga.com/tools/5-apps/12-virtual-ports.html
I assume it would be a similar process.
You'd just set up the virtual port, and in studio one you would set up spark as an external instrument sending out midi clock start / stop, etc. to that virtual IAC port.
Then you'd create a track in S1 with the output set to your spark external instrument (outputting to the virtual midi port).
In spark standalone you'd select the virtual IAC midi port as Spark's input.
Make sure you set spark to receive midi clock start stop in the options or nothing will happen. I also think there is an option
I have done this before using other midi virtual port software so I know it works, but it did take me a bit of messing around with different available options. Hope you can figure it out with a little tinkering.