Problem:

403 Permission Denied
You do not have permission for this request /wp-admin/install.php

Solution 1:

Are you using an FTP application to manage your new Wordpress files? If so, try to use CPanel instead.

Solution 2:

1. Backup your .htaccess (rename it to .htaccess.old 
2. Replace its contents with the default configuration:

Options +FollowSymLinks
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]