I believe they mean modify the contents of the file (which I think should be /etc/asterisk/logger.conf) to specify less detailed logging. You would need to decide how much logging you required, so we can’t tell you exactly what to set. You don’t have to log anything, but if you don’t, you’ll have difficulty getting help when things go wrong.
However, I suspect your real problem may be that you are not managing the logs properly outside of Asterisk. Typically you would run a cron job, possibly using the logrotate utlity, to split the file, and to delete older copies. This is something that any Linux system manager should be familiar with, as it extends to all the services run on the machine.
Asterisk has CLI commands that ensure that ensure that Asterisk closes the old file and opens the new one, after a split.
Worked examples can be found at Automatically rotate log file