I have downloaded the Flight FSX inmy windows OS. But i am clueless how to install and open it.
Taken form Steam:
How do I install FSX on steam?
To do that, go to store.steampowered.com and click the “Install Steam” button on the upper right hand corner of the screen. You should then come to this page: Click the “Install Steam Now” button to continue. Once the Steam client has installed on your computer, it's time to create an account.