Using the automatic rule update feature.

SnortCenter can automatic update new rules and push them to the sensor by using a cron job.
First make sure that in config.php on the management console the parameter:

$User_authentication = 2;

If you set it on 2, then it means that user authentication is disabled ONLY for auto update.
if you have set it to 0, then the user authentication is complete disabled and this will work ofcourse to.

Now make a cron job on the management server like:
#> curl "http://localhost/db_pars.php?source=net&push=yes"

I'm using curl because SnortCenter needs it also, but you can also use
#> wget -O - "http://localhost/db_pars.php?source=net&push=yes"

That's it.