Forum OpenACS Q&A: Response to bboard search working out-of-the-box in OpenACS 3.2.5?
If you need to install 'by hand', then you have to change that param Don mentioned, and do
su - postgres -c "createlang pltcl yourdbname" psql -q -U yourdbuser yourdbname </web/yourservername/www/doc/sql/rank-for-search.sql
too. Adjust the values of yourdbname, yourdbuser, and yourservername to match your own installation of course!