on that page say
webalizer -c test.conf -N 10 -D dns_cache.db /var/log/my_www_log
This will use the configuration file 'test.conf' to obtain normal
configuration options such as hostname and output directory.. it
will then either create or update the file 'dns_cache.db' in the
default output directory (using 10 child processes) based on the
IP addresses it finds in the log /var/lib/my_www_log, and then
process that log file normally.