Hi its great that you want to start but its really really important you read the book. Have you been on the website and found your true weight? It will also tell you how long you should stay in attack for.
Are you really sure you want to do Dukan, how much has your friend told you? Did they tell you what a long term committment it is? Its a diet you follow for the rest of your life so be sure its what you want to do. Also are you medically ok to do this diet?
I don't want to put you off but I think its really important you read the book before you start. Have a good look around this board as well to decide if its what you really want to do and are ready for the commitment. Everyone on here is really good so if you do decided to go for Dukan you're in the right place. Finally good luck!