Test if Apache is running: as root, type in the shell
service httpd status. This should inform you whether apache is running ro not. If it's not running, you can start it with service httpd start. Note that after apache installation it will be probably configured to start automatically when your computer boots up. If it's not, you should change it.
As a final test, type
http://localhost in your browser. You should see a test page or at least an error message generated by Apache at your IP address.