The whole point of having these guest machines is for testing communications, putting an IPaddress on them so you can ping things, is a pretty basic step.
1. Console in, and execute the following commands, obviously change the IP addresses to the ones you require.
ifconfig eth0 192.168.1.11 netmask 255.255.255.0 up
route add ip default gw 192.168.1.254
route add default gw 192.168.1.254