For those who are newbie like me, Open IIS, expand your server name, choose sites, click on your website. On new install, it is Default web site. Click it. On the right side you have Default document option. Double click it. You will see default.htm, default.asp, index.htm etc.. to the extreme right click add. Enter the full name of your file(including extension) that you want to set it as default. click ok. Open cmd prompt as admin and reset iis. Remove all files from c:\inetpub\wwwroot folder like iisstart.html, index.html etc.
Note: This will automatically create web.config file in your c:\inetpub\wwwroot folder. I didnt have any web.config files in my inetpub or wwwroot folders. This automatically created one for me.
Next time when you enter http(s)://servername, it opens the default page you set.