Here you can find demo database files for recent builds of DHIS 2.
The build war files are available from releases.dhis2.org.

To work with the database you can gunzip it:

gunzip dhis2-db-sierra-leone.sql.gz

Restore it using psql with a command like:

psql -d "<database-name>" -U <database-user> -f dhis2-db-sierra-leone.sql