The Horde Application Framework has been installed into
${INSTDIR}

You should point this to the DocumentRoot of your web-server:
   # ln -s ../horde /var/www/htdocs/horde
(make sure you use a relative symlink since Apache is chrooted)

and proceed to complete the installation by reading:
${INSTDIR}/docs/INSTALL

You can ensure you have a working install by accessing:
http://<localhost>/horde/test.php