a 404 Not Found error was encountered while trying to use an ErrorDocument to h

i have go through the tutorial provided here (http://codex.wordpress.org/Using_cPanel) , but i still can setup my wordpress.

i received a message
================
Not Found
The requested URL /wp-admin/install.php was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
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how should i fix it

my website is (http://kokyun.needlemen.com/wp-admin/install.php)

help