If you are using network manager, you can click on the network manager icon in the system tray, and then click on "create new wireless network"
As far as using commands, you can do the following:
Code:
sudo service NetworkManager stop
sudo iwconfig wlan0 mode Ad-Hoc
sudo iwconfig wlan0 essid my_essid
sudo iwconfig wlan0 channel 6
sudo iwconfig wlan0 10.0.0.2 up