Hi,
To setup the main primary menu
– First of all create pages from Pages >> Add new page
– Go to Appearance >> Menu
– Click on Create a new menu link
– Give a name to your menu in Menu name and click save menu button
– Once you have create menu. You need to add pages by selecting with checkboxes.
– Select menu theme locations Primary Menu from Menu Settings
– Click Save Menu after adding required pages, categories in the menu
Please check the documentation
http://gracethemesdemo.com/documentation/shifters/#header
Regards
Grace Themes