Assuming your wifi card is recognised this tool will make your life a lot easier connecting WiFi from the terminal
sudo apt-get install wicd-curses
Easy as Pi – but it will however be required every time you boot into the RPi. Quickest booting-with-wifi-approach is installing some tools:
apt-get install wpasupplicant wireless-tools
put something like this (red part is wireless config) into the /etc/networking/interfaces
iface lo inet loopback iface eth0 inet dhcp
allow-hotplug wlan0 iface wlan0 inet dhcp pre-up wpa_supplicant -Dwext -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf -B -P /var/run/wpa_supplicant.wlan0.pid post-down killall -q wpa_supplicant
generate a psk key for wpa_supplicant.conf file:
sudo wpa_passphrase YOURSSID YOURPASSWORD
you don’t want to have to write this key to a piece of paper when you don’t have internet access so to add the output tho the wpa_supplicant.conf file you do this:
sudo wpa_passphrase YOURSSID YOURPASSWD | sudo tee -a /etc/wpa_supplicant/wpa_supplicant.conf
and after that check the .conf file to see if all is there.
reboot and hope you’re ok!