Do you mean with the portfolio element? If so I’m not really sure if I can direct you to how to achieve that by adding to the built in theme options. Your best course of action would probably be to make your own page template specifically for the home page with calls to the loop to create the portfolio posts. Then add your own css specifically for that template. In essence, you’d create your own page completely separate from the theme but still making calls to include some of the functions/features of the theme.