I found a useful video on YouTube. This may help you.
https://www.youtube.com/watch?v=GMgqbufzbug
Also you want to make sure in you install the Soundcraft drivers for you board on your computer. ONce the drivers have been installed then you will need to go into the Soundcraft USB Audio Control Panel (software that is installed for the drivers). You will need to setup the Buffer Settings to match Protools. I am using ASIO Buffer Size 64 Samples in both Protools and the Si Control Panel configuration. It was a quick and dirty setup with no research or jedi mind control. You will also need to setup your I/O on each channel/track.
I hope this helped you. Now my only problem is, I am trying to playback the live recordings I just did back to the SI impact Mains. If you figure this out, please let me know. Thanks in advance !