If importing went successful, you will see menu already. To Setup menu as per your need, please go through these steps:
Main menu/ Primary menu is the most prominent menu for the theme. Mostly appears beside logo.
- Go to Appearance > Menus.
- In Manage Locations tab, you can choose the menu from dropdown list for Primary Menu.
3.If you are not seeing certain block on left side, for example Categories, please click on "Screen Options" on top right corner and select its checkbox and reload the page.
4.Always hit "Save Menu" if you are satisfactorily done modifying the menu.
Please go to Themeoptions/Header settings to select the header layout of your choice.
When you import the demo, by default the website will be multipage, if you want to have Onepage website. There are just 2 steps to do it. First, please go to Settings -> Reading and select Onepage Homepage as Front page. (First image below) Second, Please go to Appearance -> Menu -> Manage locations tab, and set Onepage Menu as Primary Menu. Thats it !(second image below)