The Configuration ⇒ LoRa network ⇒ LoRa network page only allow to choose your LoRa NwkID. The LoRa NwkID is applicable only for an OTAA fleet.
NwkID range value: 0-127.
NwkID is updated, OTAA devices already activated must initiate another join procedure to communicate again with the new NwkID
Kerlink recommends to configure the LoRa NwkID before adding your end-devices to the fleet.