To add a menu, navigate to the Menus area via Content > Manage Menus.

Click on Add Menu and enter a Name for your new menu in the Name field.

Add items to your menu by clicking the red '+ Add menu item' button:

This will add an item to the tiled list down the right hand side, highlighted in green:

The centre of the screen will now show you controls for setting where this menu item will link to, and what it will be labelled as:

You can link various aspects of your site, and even custom URLs by using the 'Item type' dropdown:

In this example I am linking a page so I have selected Page, causing a second dropdown to appear, allowing me to select a page that exists on my site already:

Once you have done this you can add an icon if you wish:

And even change the label of the menu item:

If you want to make this item a dropdown option below another menu item, use the move controls to position the selected menu tile underneath the menu item you wish it to appear under, and then press 'Move into sub-menu':

Equally if you wish to move a sub-menu out of being a sub-menu item to become a top level menu item, the button will change to say 'Move out of sub-menu'.

If the menu item you are adding is a top level menu item that you wish to add sub items to, click the green 'Add sub-menu item' button:

Once you have finished arranging the menu tiles in the order you want, click Save in the top right corner.