Qlassik

Edit your Main Menu

First click Appearance -> Menus in your Qlassik options panel. You will see that there is a select that lets you add new items. If you select one item you get a new select menu item.

Create drop down menu

Go to Appearance -> Menus and add there all menu items you would like to have in your menu. Then drag the menu item that you would like to be a submenu above the one that you would like to be main menu and release it. Do the same for all menu items and done.