To navigate to the message board, in the sidebar, go to Intranet and then Message Board.
From here, if there are topics created you can press the + button in the topics menu options to create a post in that topic or press the create a post option in the actions bar.
You are able to create a title for your post and choose what topic that this post will fall under. Additional, these posts are HTML friendly so if you have an HTML flyer, you can copy and paste the HTML into the editor using the pencil button in the toolbar.
Additionally, you can attach files at the bottom and send out notifications if you are a manager. Remember to click save when you are done!