Step 1:

Create your menu(s) and menu items. If you need help doing this, refer to this previous tutorial in which we created a Control Panel menu.

Step 2:

Go to Extensions -> Module Manager. Edit the menu for which you'd like to change the style or create a new dropdown menu for the main menu.

Step 3:

Enter these parameters:

Show Title: Hide
Position: mobile-dropdown (if TapTheme iPhone isn't your default template you MUST type this directly into the select box)

Status:  Published

Select the menu items you wish to show:

Select the Main Menu under the module parameters: