There was a reference to this doc from the old victoriametrics.com site
Tested with Release 6.9
The VictoriaMetrics DB must be place in /usr/ports/databases directory and the file /usr/ports/infrastructure/db/user.list should be modified with a new line
/usr/ports/databases
/usr/ports/infrastructure/db/user.list
866 _vmetrics _vmetrics databases/VictoriaMetrics