Add custom options to WordPress website to use (display) in your theme

functions.php

/**
 * add custom section to theme customizer (Appearance -> Customize)
 */
function worduoso_customize_register($wp_customize) {
    // add section to customizer
    $wp_customize->add_section( 'worduoso' , array(
        'title'      => __('My Custom Section','worduoso'),
        'priority'   => 10,
    ));

    // we will add 2 fields - URL and text. Of course, you can change this part to add as many as you need

    // add login link URL to customizer
    $wp_customize->add_setting('worduoso_login_link', array(
        'default'        => '',
        'capability'     => 'edit_theme_options',
        'type'           => 'option',
    ));

    $wp_customize->add_control('worduoso_login_link', array(
        'label'      => __('Login Link URL', 'worduoso'),
        'section'    => 'worduoso',
        'settings'   => 'worduoso_login_link',
    ));

    // add login button text to customizer
    $wp_customize->add_setting('worduoso_login_text', array(
        'default'        => '',
        'capability'     => 'edit_theme_options',
        'type'           => 'option',
    ));

    $wp_customize->add_control('worduoso_login_text', array(
        'label'      => __('Login Link Text', 'worduoso'),
        'section'    => 'worduoso',
        'settings'   => 'worduoso_login_text',
    ));
}
add_action('customize_register', 'worduoso_customize_register');

header.php

<?php
$login_link = get_option("worduoso_login_link");
$login_text = get_option("worduoso_login_text");
?>

<?php if($login_link && $login_text): ?>
    <div class="added-header"><a href="<?php echo $login_link; ?>"><?php echo $login_text; ?></a></div>
<?php endif; ?>