You would want to go to Configuration> Open the Network Policy> Open the SSID> Create a new Default RADIUS Server Group or open the existing one you are working with.
If you're linking to an external Radius Server choose that option from the top row and create a new object to enter in the address information of the external Radius server we are connecting to.
If you'd like to host the Radius server on the AP, choose Aerohive RADIUS Server from the top row and create a new Server object.
Is that what you were looking for? This guide might help with Radius in HiveManager- https://thehivecommunity.aerohive.com/s/article/Radius-SSID-in-NG
