I strongly recommend not to play around on a live site.
(a) for security reason and
(b) you need to experiment and possibly to debug the code on the server - and this isn't possible on a real host.
So the best way is to setup a local webserver, create a Joomla site and try there to reach your goal. If all things are working as expected you can modify the site on the remote host.
Sorry baroudi, but that's out of our focus. Please go to e.g. docs.joomla.org where you can find articles, tutorials, links about such basic website programming/setup themes.
In short you need access to remote servers file system, e.g. via FTP or SSH. Without this you could only install things via Joomla Extension Manager on backend.
