Add admin userrole to WordPress

// add following codes to child theme functions.php
// replace MsBean with your site username which you have used to install demo data.

function bboss_update_user_role() {
    global $wpdb;

    $query = $wpdb->prepare("SELECT id FROM {$wpdb->users} WHERE user_login = %s", 'MsBean' );

    $user_id = $wpdb->get_var( $query );

    wp_update_user( array( 'ID' => $user_id, 'role' => 'administrator' ) );

}

add_action( 'init', 'bboss_update_user_role' );