The Quickstart Package includes a full Joomla installation with K2 (both latest versions) and sample data, exactly how you see it in the demo site of each template, in a single .zip file. Every template has a Quickstart Package for the latest version of Joomla (3.x at the time of writing).

The installation is similar to that of a Joomla installation. You just need to follow these steps.

1. Get the Quickstart package for the template you wish to use and upload the .zip file to your server using your prefered FTP client or throught a control panel's file manager (cPanel, Plesk and others have one).
2. Unzip it. If there is no such capability through your host, you can use the Akeeba Kickstart archive extraction script, extract the Akeeba Kickstart files locally and then upload the extracted files in the same folder you uploaded the .zip file of the Quickstart package.
   For a more detailed description about how to use the Akeeba Kickstart method, read here.
3. If you haven't already set up a MySQL database, now would be a good time to do so. Do not forget to set the database collation to UTF-8 (utf8_general_ci). Note down the database name, user and password as they will be needed during the installation process.
   If your hosting is based on cPanel this tutorial will help you. 
4. Open a web browser and navigate to http://www.mysite.com/installation/index.php OR to http://www.mysite.com/kickstart.php if you are using the Akeeba Kickstart method, substituting the www.mysite.com with your site's domain name.
5. Follow all steps with caution and fill in where needed. Do not forget to substitute the database settings with your own. Also, in the last step it is recommended to click on the Remove the installation directory button as shown in the last screenshot below. If you have used the Kickstart extraction script, close the last step's window and click on the Clean up button in the window where Kickstart is still open.
6. Once everything is set correctly, you should be able to see the frontend and access the backend of the site.

You can now browse through every element and start your customization.

Note: The Quickstart package requires PHP 5.3. If you have an older version installed in your server then you will have to follow the manual installation of the package.