How to Set an IP address to an interface ?

with the command ifconfig -a you’ll see all the network interfaces which are installed.
To set an IP address make:

$ ifconfig "interfaces" x.x.x.x netmask x.x.x.x
$ ifconfig ath1 172.0.0.2 netmask 255.255.255.0 up

these commands as root.
T0 set a default gateway

$ route add default gw x.x.x.x

To add the dns resolve address locate the resolv.conf file and write them on it.

$ nano /etc/resolv.conf
nameservers 200.00.00.00

save and close.
sooo ping google.com