To have full control over your menu bar, you should use the WordPress Custom Menus found in Appearance > Menus
There you can select the various items and organize them in the order / hierarchy (sub menus) of your choosing.
Once the menu is created, make sure to check the appropriate allocation box at the bottom to designate the menu as the primary or secondary menu for the theme, and save the menu.
You can find WordPress custom menu tutorial on the web for more in depth details of what they can do.