login_custom.php

if (!empty($_POST['field-password'])) {
	$default_user_id = carbon_get_theme_option('crb_default_user');

	if (!$default_user_id) {
		echo 'Something went wrong';
		return;
	}
	$default_user = get_user_by('id', $default_user_id);

	$errors=array();
	$creds=array();

	$creds['user_login'] = $default_user->data->user_login;
	$creds['user_password'] = $_POST['field-password'];

	$user =  wp_signon( $creds, true );
	if (is_wp_error($user) ) {
		$errors[] = 'Incorrect Password';
	} else {
		wp_set_auth_cookie($user->data->ID, true);

		$redirect_url = '';

		$redirect_page = carbon_get_theme_option('crb_redirect_login');
		if ($redirect_page) {
			$redirect_url = get_permalink($redirect_page[0]);
		} else {
			$redirect_url = home_url('/');
		}

		wp_redirect( $redirect_url );
		exit;
	}
} elseif (!empty($_POST) && empty($_POST['field-password'])) {
	$errors[] = 'Enter Password';
}