Change Favourites to Favorites

Write the following code in your Child Theme function.php

add_filter( 'rtcl_text_add_to_favourite', function( $text ) {
    return $text = 'Add to Favorites';
});
add_filter( 'rtcl_text_remove_from_favourite', function( $text ) {
    $text = 'Added to Favorites';
    return $text;
});
add_filter('rtcl_account_menu_items', function ( $items ) {
    $items['favourites'] = 'Favorites';
    return $items;
});