The Network Settings section specifies Address IPv4, mask and gateway for this device.To force the use of DHCP, you need to set the IPv4 Address to 0.0.0.0.
The changes will take effect only after the device is restarted.
The second section is the "white" list of IPv4 addresses of devices (clients) for which the block control via ModBus TCP is allowed. The block will not respond to all other clients.
You can set the broadcast Address 192.168.1.255, then control will be allowed for all device addresses in the specified subnet.