If the .htaccess file is not writable, in order for Hide My Wp Ghost to work you need to write the code you receive in the Hide My Wp Ghost > Permalinks after you change the settings.

If you don’t have server access you can install a plugin that will help you with this:
https://wordpress.org/plugins/wp-htaccess-control/

You can remove the wp-htaccess-control plugin after you’re done with the setup.