1. Navigate to Services | DHCP Relay.
2. Check the Enable DHCP relay on interface checkbox:

3. Select the interface on which the DHCP relay will be applied. Hold down the Ctrl key while clicking on an interface in the list box to select multiple interfaces.
4. If you want to append the circuit ID and agent ID to DHCP requests, check the Append circuit ID and agent ID to requests checkbox.
5. Enter the IP address of the existing DHCP servers to be used in the Destination server edit box. Multiple IP addresses may be entered, separated by commas.
6. Click on the Save button when done.