Posting on the main site

Hi! I’m looking for a solution of my problem with multisite posting. I’ve just launched a multisite application for a school where I’m working. It has a main site and six other sites for each particular program of the school (machinery, electronics, computers, etc.). Each of this site is edited, posted by teachers who doesn’t have much computer knowledge. The intention is to post news on a local site and on a main site.
I found your plugin which should do this kind of service but I cant’ select to publish the post on the main site. I mean when I publish the post on the site of my school and I want to publish it on the main site also, it doesn’t display the option which I could select.
Have I missed something?

https://www.ads-software.com/extend/plugins/diamond-multisite-widgets/