Quite easyOn the existing installation perform a
mysqldump -u tikiuser -p tiki-db > dump.sqlor use similar in phpmyadmin.
On the new run
mysql -u tikiuser -p tiki-db < dump.sqlor similar in phpMyaadmin
Now, you will need to copy over any file, image, and forum directories that are setup, also copy over img/wiki_up , games?, custom themes in styles/ and templates/styles/ to the new installation.
That should be it then