If you've installed dokuwiki without running install.php, you will be able to create and edit new pages, but you will not be able to access the administration pages, because there is no admin (superuser) and no ACL set for the wiki. If you haven't run install.php as yet, there is a good chance you can still run it and set up your wiki. Once you've done that, you will be able to access the admin pages, which includes the config manager, where you can turn on html using the htmlok setting.
When you run install.php, enable ACL.
Enable ACL (recommended)