Step 1:
Create a menu. Add menu items of the type "Menu Heading" for any large, left-hand headings that you'd like to be included.
Step 2:
Create children links for each menu heading.
Step 3:
Create a module for the menu you have created. Add the class middle-menu to the "Menu Class Suffix" field. (found under the "Advanced" tab). Make sure there is a space before the class name.
Step 4:
Place the menu on the page. This can be done by putting the menu in a module position (full1 for example) and assigning it to the appropriate menu item. You can also place the menu directly within an article by selecting the module button at the bottom of an article and selecting the middle menu you created.