Well, it's not intuitively obvious, that's for sure, but it's not hard, either. I'm not absolutely certain, but I'm going to assume 8 channels is the default here. First, insert your Jamstix VST and enable All Synth Outputs. That should give you a default of 8 Jamstix tracks in X1. Then, open the Jamstix GUI, and go to the mixer tab. You should see a default of 8 channels displayed.
In the top part of the mixer screen you should see the kit displayed. Up in the top left is the name of the kit, and a little drop-down arrow ... drop down that arrow, and it gives you options for how you want to set your output routing. Select one of the options (the numbers in the names refer to the number of channels you are setting up). To see what is set up on the mixer, hover over the channel number and it will tell you what the channel represents: Channel 1: Kick, Channel 2:Snare, etc. Each channel should now correspond to an associated track in X1.
If you need more (or less) than 8 channels, go to the Options tab in the Jamstix GUI and set Audio Outputs (Stereo) to something more than 8. I haven't tried this myself, but I don't see why it wouldn't work.
Good luck!
"Surf music will never die." -- LeapinLizard, 1963
"We may never hear surf music again." -- Jimi Hendrix, 1967.