First thing you need to do, is find out where httpd.conf is located.
You might need to perform an update on the locate database first, so log in as root and type the following:
After that is complete type:
It should show you the location.
Next type cd locationtohtppd.confhere (where that is the location it is located at.)
Once you are in the proper directory (probably /usr/local/apache/conf/) you can do a ls to make sure httpd.conf is located there.
You can edit at will.
Caution, I would make a backup before making any changes by hand.
You can do this by typing in the directory where httpd.conf is located:
cp httpd.conf httpd.conf.old