How can I add specific text in each article sidebar?

Hi dear WP staff

I’ve a problem that I’m not able to solve. I’ve bought MH Themes last year and now I’m creating a website with MH Squared. Whenever I create an article, I would see a specific box in the sidebar (different from the global sidebar) on the right, titled “Dettagli dell’iniziativa”, in which I can add every time a different text. How is it possible? Should I download a specific plugin? It would be useful to do this directly in the article editor …………./wp-admin/post-new.php.

Thanks,

Giambattista