To add a menu on your Wordpress.com site we've added a convenient short-code to your customization dashboard. If you do not know if you're using Wordpress.com, or Wordpress.org, this article will help.
Log in to grab the short-code for your menu:
Click Customize Menus on the sidebar
Then select Website from the menu on top:
Copy and paste the shortcode into the Wordpress.com page where your menu should appear. Save, publish, and enjoy your beautiful new website menu.