Adding menu / navigation links
During the Theme Setup steps a menu will automatically be created for you. You can find this under WP Dash / Appearance / Menus /
Creating and editing menus
Creating and editing options are available via the WordPress menu WP Dash / Appearance / Menus /
Please see: WordPress Menu User Guide
Missing menu Items
Some items such as "Custom Post Types" might be hidden so that you cannot add them as links. To show them, click the "Screen Options" tab a the top, and check the appropriate box to show them.