cannot add WP admin

I’m currently redesigning a site, and attempting to do it through wordpress, yet I have gone to hell and back trying to figure out what I’m doing wrong. The site I’m redesigning is still active (connected.ie), but I cannot edit it through wordpress at all. I received emails through DreamHost, our new hosting site, that wordpress was in fact installed on the site, but whenever I try and click on the links to access the site (http://www.connected.ie/wp-admin/install.php) all of the links come up with the same error: Not Found

The requested URL /wp-admin/install.php was not found on this server.

I simply don’t know what to do next. Help please!!!