Step 1 Open .info file and declare the styles for Superfish with this rule:
superfish_styles[style_name] = Extend style for Superfish
Example Let's extend the style for Superfish in TB Simply theme. Just add this line:
superfish_styles[simply] = Simply Style for Superfish
Step 2 Add style sheet css/superfish/simply.css
Step 3 Extend style of class sf-style-simply
Backend Take a look at the Superfish configuration in the back-end.