You have to edit crontab. It's really nothing more than a text file that is parsed for commands.
crontab -e
Now insert the cron entry
0 9 * * * service httpd restart
Save it, and it should start doing that every morning at 9. You should be passing full path commands to crontab though. I use apachectl, so mine would look like this:
0 9 * * * /usr/local/apache2/bin/apachectl restart
