Navigate to Appearance -> Themes -> Add New -> Upload Theme. Select file. Press Install Now button to upload and install the theme: 

After that, you will have to activate the theme: 

Wizard will ask you to install theme required plugins. Click “Begin activating plugins” and it will install and activate all required plugins.

In Bulk Actions choose Activate option and press Apply:

Finally, you will need to import demo data, just  choose this option in Customize

Click on Import button and all required demo data will be imported:

There is the last step – setting menu. Go to Appearance -> Menus. All you need is to click on "Primary menu" and save these changes:

That’s all! Theme required plugins were installed and demo content was imported.