Hello Proline,
Welcome to the Forum.
I assume you have bought it from the shipsim.com website. If so, what I have mentioned below holds good.
First and foremost have you created an account for yourself at the www.shipsim.com website ? You can do this by clicking on "Register" (at the top left corner). You will have to create a log-in ID and a password.
Once you have this, log in. You will then be taken to an "Account Management" page. Here, you click on "Orders & Downloads". In the "Orders & Downloads" page, you will see "Ship Simulator 2008 CE" under "Downloads Overview". Click on this and you will be presented with a .exe file which you have to save (in any location of your choice). Install it from there. In the same page you will also see the License Key under "License Key" overview, which you will need during the course of installing SS 2008 CE.
This is the right way to install the software. Please feel free to ask further questions if required.
Further, after successful installation, please register your License Key in your Profile in this Forum
Regards
vin_sun