how do you connect a NAS hard drive to an apple express using ethernet

I have a new apple express (n model w/ 2 LAN ethernet ports) and I purchased an iomega EZ 2T NAS HD and want to be able to stream or download videos/movies to an ipad wirelessly either in home using the airport's wireless network or through the internet when connected to another network. I used the 2nd port on the AE but was unable to set the NAS up. In order to go outside the local network, I need to use "port forwarding." I am unable to do this. Appreciate any assistance.