The CSS panel mentioned in the Settings section can be used to style outline text by level. For example:
font-family: Arial !important;
font-weight: bold !important;
margin-bottom: 8px !important;
Will make the top level heads bold and in Arial font and will add 8 pixels after every level.
Another example, if you wanted to provide a background image to "skin" the Fargo app, you would add this bit to the CSS text.
To learn more about how this works, for styling experts, have a look at the generated HTML instructions in a good debugger.