If you connect directly to a PC using a crossover ethernet cable, you can then use the Device Discovery Utility to discover and configure the unit. Another option is to connect the unit to a network running a DHCP server to assign an IP address. However, these units do not ship with an IP address by default so you cannot connect to the unit directly until one has been assigned.
Alternatively, you can by connecting directly to the serial port using a null-modem/crossover cable.
Login as root, then issue the "set network" command to configure the IP address.