You should not edit conf files directly. If you do, things will revert back to what they were, and your changes will be lost.
What you need to change is http.conf, and it needs to be changed using the template system.
If you follow the steps below, it should get the results you are looking for.
I recommend using something like "putty" to connect to your server. that will allow you to use copy and past most of the lines below.
I beleive this should give you what you want, or at least a good start.
cd /
mkdir -p /etc/e-smith/templates-custom/etc/httpd/conf/httpd.conf
cp /etc/e-smith/templates/etc/httpd/conf/httpd.conf/50DirectoryIndex00 /etc/e-smith/templates-custom/etc/httpd/conf/httpd.conf/
pico /etc/e-smith/templates-custom/etc/httpd/conf/httpd.conf/50DirectoryIndex00
add portal.php to the list of items in the line that starts with DirectoryIndex
exit with save. (clt-x, y, enter)
Expand the template
/sbin/e-smith/expand-template /etc/httpd/conf/httpd.conf
restart apache
apachectl restart
If it messes things up too badly, just remove the template fragment, re-expand the template and restart apache.
Bob