Import the Alexander Theme-demo.xml file which you will get from the Alexander WordPress Theme Pack. To get the Theme installed as shown in the demo you need to import a .xml file into your WordPress dashboard.
Go to Dashboard from the left Sidebar menu Tools > Import. run the importer from the WordPress option.
Click on upload file and import, choose your .xml file, and click on the Upload file and import button. Then assign your author from an existing user (or) a new user and click on Submit.
Now your file is successfully imported that you need to enable Main Menu, click on customize (present in the top bar), a left sidebar will appear select Menus option
Then select Main Menu scroll to the bottom you will see Menu location set Primary now your Menu is ready.