Hello kevintruex100,
I do have the NSI Key when using Cisco 3600 AP.
If your AP is in standalone mode, go to Network > Network Interface and select the radio interface (Radio0-802.11N 2.4GHz or Radio0-802.11N 5GHz. After that select Settings and than Spectrum.
This will do the AP work as a Spectrum Analyzer.
Click on Spectrum Information and you got the NSI Key.
Regards.