The PC Dialer can be downloaded through the official website. You will have to access the website, then after it loaded, click on the upper button called PC Dialer. A new page will load and then you will have to download one of the three dialers available. Notice that each one is used for another network. Download the application that you need based on the pre-paid card you have acquired because not all the presented apps will work.
Download page: http://www.ksafone.com/pc/pc.php