There is no simple answer to that. If you have acs-developer-support installed, there is a developer support tool bar that provides a link to the tcl shell (/ds/shell). You need to be site wide admin to access this area.
Also the user that is used from the aolserver to connect to the database requires to have the right priveleges. Then you could, in case you know where the ltree sql is located execute that from the shell using
exec psql < ....
You could try to search for the ltree file from the shell using exec as well. With exec you can execute linux/unix commands from within tcl so you could try
exec locate ltree.sql
if findutils is installed or
exec find / -name 'ltree.sql'
But to be honest I would recommend contacting the system admin for help.
