To use jar add the jar to your CLASSPATH 
variable or specify it when you start java. 

java -classpath skinlf.jar TheMainClass 

To enable skin u can add this in main: 
com.l2fprod.gui.plaf.skin.SkinLookAndFeel.setSkin(com.l2fprod.gui.plaf.skin.SkinLookAndFeel.loadThemePack("c:\aquathemepack.zip")); 
com.l2fprod.gui.plaf.skin.SkinLookAndFeel.enable();
