I have an iPhone
Please download the Jitti application from the AppStore.

I have a Windows Mobile
The Jitti client needs to be downloaded and installed onto your smartphone.
To do that, start the web browser on your phone, and open the download webpage (http://ws.jitti.hu/ts/hu/Download.htm). (If typing this text is not comfortable, than on your phone, using the browser, open the www.jitti.hu webpage, and select the Download item.)
A detailed installation guide is available here.

When you first start the client, you'll have to register yourself as a Jitti user, using an e-mail address and a password.