Redirect non-members to about/intro page

Open your theme’s headr.php file and add at the top

<?php
if( !is_user_logged_in() ) {
    wp_redirect(get_permalink(123));
    exit;
}
?>

just change 123 to the id of your about page, or replace get_permalink(123) with the about page URL example:

<?php
if( !is_user_logged_in() ) {
    wp_redirect('http://mydomain.com/about');
    exit;
}
?>