functions-theme-opt.php

<?php 

/**
 * Adding additional options in Genesis Theme Settings page for gathering a comma sep list of excluded categories 
 * Thanks to @author Bill Erickson for the jumping off point! 
 * @link http://www.billerickson.net/genesis-theme-options/
 * @package yourthemenamehere
 */

/**
 * Step 1: Register Defaults
 * @param array $defaults
 * @return array modified defaults
 */

function kl_options_defaults( $defaults ) {

	$defaults['exclude_categories'] = '';
	return $defaults;
}
add_filter( 'genesis_theme_settings_defaults', 'kl_options_defaults' );

/**
 * Step 2: Sanitization
 * Register our option values with the no_html sanitization type defined within Genesis.
 */

function kl_register_option_sanitization_filters() {
	genesis_add_option_filter( 
		'no_html', 
		GENESIS_SETTINGS_FIELD,
		array(
			'exclude_categories',
		) 
	);
}
add_action( 'genesis_settings_sanitizer_init', 'kl_register_option_sanitization_filters' );

/**
 * Step 3: Register additional metaboxes to Genesis > Theme Settings
 * @param string $_genesis_theme_settings_pagehook
 */

function kl_register_option_settings_box( $_genesis_theme_settings_pagehook ) {
	add_meta_box( 'kl-option-settings', 'Exclude Categories', 'kl_option_settings_box', $_genesis_theme_settings_pagehook, 'main', 'high' );
}
add_action( 'genesis_theme_settings_metaboxes', 'kl_register_option_settings_box' );

/**
 * Step 4: Option Settings Metabox Callback
 * @see vg_register_option_settings_box()
 */

function kl_option_settings_box() {
	?>

	<p><?php _e( 'Exclude these categories from the main post loop (Comma separated - 1,2,3 for example):', 'jharrison' );?><br />
	<input type="text" name="<?php echo GENESIS_SETTINGS_FIELD; ?>[exclude_categories]" value="<?php echo genesis_get_option('exclude_categories'); ?>" size="50" /> </p>

	<?php
}

/**
 * Remove Metabox for the blog page template from the options page
 * because we prefer users to use the one above
 * This removes unused or unneeded metaboxes from Genesis > Theme Settings. 
 * See /genesis/lib/admin/theme-settings for all metaboxes.
 *
 * And another thanks to @author Bill Erickson
 * @link http://www.billerickson.net/code/remove-metaboxes-from-genesis-theme-settings/
 */

function be_remove_metaboxes( $_genesis_theme_settings_pagehook ) {
	remove_meta_box( 'genesis-theme-settings-blogpage', $_genesis_theme_settings_pagehook, 'main' );
}
add_action( 'genesis_theme_settings_metaboxes', 'be_remove_metaboxes' );

functions.php

<?php 

// Include theme options
// UPDATE THIS TO THE CORRECT DIRECTORY!

require get_stylesheet_directory() . '/inc/functions-theme-opt.php';


/*
 * Add functionality to exclude categories to the metabox added to theme settings 
 * Box added to theme settings in /inc/functions-theme-opt.php'
*/

function kl_exclude_categories_from_loop($query ) {
  if( $query->is_main_query() && $query->is_home() ) {
	    $query->set( 'category__not_in', genesis_get_option( 'exclude_categories' ) );
  }
}
add_action( 'pre_get_posts', 'kl_exclude_categories_from_loop' );