Concrete5 needs to be installed directly on a web server, or in other words, directly in your hosting account. You will want to download an FTP client (I use filezilla), and use the username and password provided by your web host to upload the files in the concrete5 package.

http://filezilla-project.org/

Sometimes the username and password for ftp is slightly different from what you would use to log in to your web host. Once you have filezilla installed, you will want to type in the domain name in the host box, and the username and password in those respective boxes, and connect. I'm not sure how it works with fatcow, but you should see a folder structure on the right side, you'll want to make sure you move the files you downloaded for concrete5 into a folder which will most likely be called public_html

If you have anymore issues feel free to let me know, and I will follow up.

Thanks,
Benjamin Brinkman