Fxam on "Custom Order Portfolio Filters Marble Theme"

Hi, I need help changing the order in which my portfolio categories appear on my site. http://newpage.felipeascacibar.com/

I have learnd that it is possible to:
'orderby' => 'slug',
changing the code in "portfolio.php"
but the theme I'm using doesn't have a
portfolio.php!?
I found some code in "theme_actions.php" but I cant figure out how to make it sort by slugs. Please Help!

/*
* Displays the isotope filters for the portfolio
*/
add_action( 'ebor_portfolio_filters', 'ebor_portfolio_filters_markup', 10 );
function ebor_portfolio_filters_markup(){
$output = '';
$output = '<ul class="filter">

';

$categories = get_categories('taxonomy=portfolio-category');
foreach ($categories as $category){
$output .= '

';
}

$output .= '';
echo $output;
}
/*