radiusd -d help

I have installed freeradius successfully under /etc. I was inform by supervise to install under /opt/freeradius instead. I was informed to use radiusd -d to tell the freeradius server where to look for the configuration files, but I am not familar with the handle -d. I am just doing authentication against an AD server. I know that I am going to need sbm.conf and krb5.conf files in order to run freeradius succesfully, but they are in the /etc directory and freeradius is in the /opt directory. So how do I tell freeradius where to find these files if freeradius is install in a completely different directory using radiusd -d?