Ok sorry,
so open the terminal on your N9,
then write : "devel-su" and as password "rootme".

After that, write :
nano /usr/share/themes/base/meegotouch/libsysuid-screenlock-nokia/style/libsysuid-screenlock-nokia.css

Then with the arrow move to the line under "LockScreen MImageWidgetStyle#LockScreenLowPowerModeOperatorLo go"

and change the lines.

Note that nano is the text editor that i'm using.
( Sorry for my spelling, i'm not english)