The non NI PXI has a controller (aka computer) and the NI VNA driver must be installed on that controller before installing the NI VNA. You can download the NI VNA driver from ni.com/drivers, then type VNA in the search window. As part of this driver installation, MAX (configuration utility) will be installed on the controller as well.
I must admit I have never used a non-PXI chassis. However, I'm pretty sure that the non-NI chassis should show up in MAX and that the NI modules within the chassis should appear there as well. Have you tried this? What controller are you using with this chassis? When the system is turned on, the controller discovers the bridges and modules connected to it, and tries to locate and load the right module drviers. This discovery process is not NI technology, so it should work regardless of the controller and chassis, assuming it was implemented correctly by the chassis and controller/PC manufacturer. NI works very hard to make sure we stick the standards. We have found 3rd party controllers (especially consumer PCs) that do not comply with the standards. Let me know what you are seeing.