Step1: Choose the template and get into the builder.
Step2: 2nd last tool of the toolbar at the left corner of your page reads 'MENU'. Click on it and the menu will be added to your page at the top.
Learn more through video: https://s3-us-west-2.amazonaws.com/meetzippyandhqmeetuptokboxrecording/46351292/031ac36b-0fa3-469d-ae55-263449d829ba/archive.mp4