Setting up Wireless Networking
Wireless networking on Linux can sometimes be quite hard if you don't know how to do it. Since you will start in a CLI interface it will be slightly harder to do. It is assumed that you haven't set up a user yet.
Unencrypted Networks
Unencrypted networks are the most easy to connect to. First run
iwconfig
and look out for some output. Next to the one with the chunk of information, there should be something like "wlan0" or "eth1". If there isn't, you haven't set up yet. Have a look at the Arch Linux wiki. Remember this, as you will need it later as "[network-interface]".
Now you will need to connect to your network. If you don't know what your ESSID or SSID is (basically the name of the wireless network), run
iwlist scanning
and look for your wireless network.
Run
iwconfig [network-interface] essid [your-essid/ssid]
now run
dhcpcd [network-interface]
If it outputs nothing, your network is now up! Try running something like
ping google.com
WEP (Wired Equivelent Privacy) Encrypted Networks
WEP Encryption
It is not recommended to use WEP encryption because it is so insecure. It can be hacked in a matter of minutes! Please use WPA.
WEP is not much harder to set up. First of all run
iwconfig [network-interface] essid [your-essid] key [your-wep-key]
and then run
dhcpcd [network-interface]
You should then be able to use the internet!
WPA (Wi-Fi Protected Access)
WPA will be a bit harder to set up. An easier way is to use the new netcfg scripts. You will need internet access for this to work! First install netcfg
pacman -S netcfg
Open /etc/network.d/wireless as root. Put in
CONNECTION="wireless"
INTERFACE=wlan0
SCAN="yes"
SECURITY="wpa"
ESSID="mynetwork"
KEY="SomePasskey"
IP="dhcp"
TIMEOUT=20
And edit the information to your network. Now run
netcfg wireless
If it runs successfully, your internet connection should now work!
Info
You've already done half of what you need to do next 
Getting it to connect at boot
This is the easy bit. See the following page for more information: