Open MainMenu for editing. Position the cursor where the item is to appear and type in the name of the tiddler. If the tiddler's name is a WikiWord it will work automatically as a link. If not, insert two square brackets either side of the tiddler name: <code>[[tiddler name]]</code>.
Close MainMenu. You should now see the new item displayed.
Close MainMenu. You should now see the new item displayed.