Hi the HTML editor is found on your post or page editor while you are logged into WordPress and creating a new pager, post or editing the content.
You will see two tabs on the top right hand corner of the editor next to the top tools menu. These tabs allow you to change between the WYSIWYG and HTML.
The free version of this plugin only allows you to add the shortcode while you are working with the HTML editor....if you then change back to the WYSIWYG editor you will most probably loose the settings. If you want to work with both editors you have to purchase the PRO version.
I hope this helps you. If it does and it has resolved your issue can you mark this support ticket as resolved.