Hello,
It depends on how the site is setup. Usually, there is a repeater on the main page, where the news are displayed. This repeater displays documents (in this case news or message) automatically, if they are placed in the correct folder. Basically, you need to find out, how the messages are displayed. Go to
CMS Desk / Content / <navigate through the content tree to the page, on which the messages are displayed> / <identify the web part, which displays the news> / <edit the web part> / <check the path property of the web part, if there is any> / <navigate through the content tree to the location, specified by the path property>. If you find all the previous "messages" in this location, you can create a new one by clicking the "New" button on top of the content tree and create a new "message".
If this doesn't help you, please post a screenshot from the CMSDesk of the page, which displays the messages.
Best regards,
Boris Pocatko