Tikiwiki has been installed into ${INSTDIR}

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

*** First install
To complete the installation, make sure you read
${INSTDIR}/README.OpenBSD then point your web browser to:
http://<hostname>/tikiwiki/tiki-install.php

*** Upgrade
To complete the upgrade, you must update your database schema using the
scripts under ${INSTDIR}/tikiwiki/db/.
Make sure to read the official documentation at:
http://tikiwiki.org/ReleaseNotes20#1_9_x_to_2_0_migration_tips