Create a text field in the Customizer and show it in the front end

1) Add this to your functinos.php

// =========================================================================
// REGISTER CUSTOMIZER - PANEL, SECTION, SETTINGS AND CONTROL
// =========================================================================
function theme_name_register_theme_customizer( $wp_customize ) {
    // Create custom panel.
    $wp_customize->add_panel( 'text_blocks', array(
        'priority'       => 10,
        'theme_supports' => '',
        'title'          => __( 'Text Blocks', 'theme_name' ),
        'description'    => __( 'Set editable text for certain content.', 'theme_name' ),
    ) );
    // Add section.
    $wp_customize->add_section( 'custom_title_text' , array(
        'title'    => __('Custom Text','theme-name'),
        'panel'    => 'text_blocks',
        'priority' => 10
    ) );
    // Add setting
    $wp_customize->add_setting( 'title_text_block', array(
         'default'           => __( 'Default text', 'theme-name' ),
         'sanitize_callback' => 'sanitize_text'
    ) );
    // Add control
    $wp_customize->add_control( new WP_Customize_Control(
        $wp_customize,
        'custom_title_text',
            array(
                'label'    => __( 'Custom Text', 'theme_name' ),
                'section'  => 'custom_title_text',
                'settings' => 'title_text_block',
                'type'     => 'text'
            )
        )
    );
 
    // Sanitize text
    function sanitize_text( $text ) {
        return sanitize_text_field( $text );
    }
}
add_action( 'customize_register', 'theme_name_register_theme_customizer' );

2) Show in the Front End with a hook

function add_custom_field(){
    echo get_theme_mod( 'title_text_block');
}
add_action('genesis_site_description', 'add_custom_field');

In this case I’ve placed the custom text in the site-description, but You can put it anywhere You want using the Genesis Visual Hook Guide.