Error 404 when Installing WordPress

Thanks in advance for the help. I am building a brand new website for a client who currently uses Joomla. Their existing site is currently hosted on Cox Communications. I am required to create a new folder in their existing file manager to begin building the new website in wordpress.

I have done that and then uploaded WordPress and the theme I am using. I am unable to complete the installation however. I go to http://www.hcci-ks.org/wp-admin/install.php and get an Error 404 An error has occurred.
The requested page cannot be found.

I need to get started to build this site. Any information would be incredibly helpful in getting this taken care of.