In the menu properties window click on the “Edit menus...” button. A dialog will let you edit your menu. Use the “Add” button to add items to the menu; enter the label, an optional name and help string. You can use numbers or variable names as the item id. If you use a variable name, you have to provide extra code in the generated source code.

Choose the type of the item: Normal, Checkable or Radio.

You can move menu items with “Up” and “Down” buttons, and you can modify the hierarchy of the menu with “<” and “>” buttons.