There’s nothing built into the plugin for that, so it’s really up to you.
You could use a custom post type, category or tag, but you’ll need to structure the query for your blog to suppress those posts. There should be some articles in the codex or online about how to do that.
Another options might be to set the post status to ‘draft’ or a similar status that would not normally be visible. You can then include that status in your query, using the ‘post_status’ argument: