Go to Admin > Manage Styles
Click the Create tab.
Type a name for the new style.
Scroll to the bottom.
Click the save button.
Click the Modify Style tab.
Choose the style you created
Click Pick Style
Scroll to the bottom
Erase the existing css
Paste the new code in.
Click Modify Style
To use your new style:
Choose it in the dropdown
menu from Manage Styles.
Thanks,
Nottz.