Classified Ads website. how to start?

[eluser]Sinclair[/eluser]
Hi, I'am new to codeigniter.

I need to develop a Classified Ads website using codeigniter, but I don't know how to start this project. I read about codeigniter do not need to use models, so my question is: I nee to write a class like "Class Ads"? What should be my aproach to this using codeigniter?

Sorry for my bad english and my newbie questions.

Best Regards, André.