You can change the root directory, or you can take one of my virtual host and use it as an example:
<VirtualHost *:80>
ServerName natesblog.us.to
DocumentRoot "/Program Files/Apache Group/Apache2/htdocs/blog"
ServerAlias www.natesblog.us.to
</VirtualHost>
Servername is the name you want to name it (I believe this can be anything), DocumentRoot (obvious), and ServerAlias is where you put the url to that site (use a space for mutiple urls like "www.natesblog.us.to natesblog.us.to").