As seen in our Reference Manual under section 16.1.9:
"Motion constructs are used with tracking protocols. Each motion construct represents a trackable object. Associate the Motion Fixture property of objects with a motion construct to link them with the tracking data."
PosiStageNet is your tracking data, and provided you have set it up correctly on the network and Capture receives it, then it should work right away. Depending on your network configuration you might need to change in the Capture tools\options\connectivity the setting of Automatic to the specific network that PSN uses in your setup.