On RH 8.0 out of the box...
Using an xserver app (gnome or kde) goto "EDIT RUNLEVEL" ensure that the HTTP service is configured to start at your runlevel (5 for GUI, 3 for command line).
Also make sure that the MySQL service is started. You may have to download hte PHP_MYSQWL*****.rpm and install them (just double click).
Apache will automatically be configured to listen to all ip's on port 80. Unless you are doing something funky...this is correct.
on redhat 8.0 you dirs will be
/var/www/html for apache published files
/etc/php.ini for your php.ini file
if apache is started and you goto a browser and tpe 127.0.0.1 and get nothing, then either your apache config is bad or your local loopback is misconfigured. During boot watch the lines as they pass the screen and make sure you do not get any "FAIL"'s.