I need a bit of help with aircrack-ng

Okay, so I am new to linux and I want to use aircrack-ng.

I type: ifconfig wlan0 down... It works like it's suppose to

ifconfig wlan0 mode monitor... It says... ifconfig wlan0 mode monitor
mode: Unknown host


I can't get it to work, please help me.
I am using a Belkin wireless adapter for wifi connection if that helps any...

ifconfig is not meant to enable or disable monitor mode
iwconfig is but you'd better use airmon-ng
You should check aircrack-ng wiki, this is all explained and where you should start your journey into the wifi hacking world ;)