add new user to use sudo

1.confirm sudo posistion of ports collection
#whereis sudo

2.install sudo with log function
#cd /usr/ports/security/sudo
#vim MakeFile
remove -disable-log-wrap
#make install clean

3.use root to add user and enable sudo log
#visudo
add new lines as below
Defaults syslog=auth
Defaults log_year,logfile=/var/log/sudo.log

4.enable syslogd service on /etc/rc.conf
#vim /etc/rc.conf
syslogd_enable="YES"

5.start syslogd service
#/etc/rc.d/syslogd start