Comment 21 for bug 615892

How can I create a /etc/xorg.conf file with:
Section "InputClass"
        Identifier "Mouse Remap"
        MatchProduct "Saitek Cyborg R.A.T.7 Mouse"
        MatchDevicePath "/dev/input/event*"
        Option "ButtonMapping" "1 2 3 4 5 6 7 2 9 10 11 12 0 0 0 16 17 18 19 20 21"
EndSection

Sorry guys but I'm new to Ubuntu... So if you can write the procedure step by step, I'll be grateful.