The Demo is a joomla 1.5 complete installation, and includes everything you see in the demo. The demo is installed the same way as you installed Joomla. If you would have installed the demo. The site would of been identical.
IMPORTANT: Things you need to know!!!
You need to make sure your database uses mysql5, it wont work trying to install it on mysql4.
Also make sure you unzip the file. And look for the folder that contains Joomla 1.5 its the News_Line_15_Demo folder. When you unzip it, look inside to make sure you have the right folder to upload to your server.
Also read this post.