Modbus RTU over TCP/IP in CitectSCADA 6.1

I have the following hardware:
MultiRail RTU Power Meter (http://www.selcousa.com/railrtu manual.pdf)
Lantronix UDS1100-IAP External Device Server (Serial to Ethernet)(http://www.lantronix.com/device-networking/external-device-servers/uds1100-iap.html)
PC with CitactSCADA 6.1.

I would like to connect the MultiRail RTU Power Meter to the Lantronix UDS1100-IAP External Device Server and connect it to a switch connected the Citect server. How would I go about configuring the comms in Citect to read the registers from the slave device?
Would anyone be so kind as to run me through the steps to setup I/O Device, Ports and Boards, please?

Many thanks.