How to create .msi using installshield 2013 from a existing .ism file.

Hi,

I have a .ism file created already using installshield 2012 version. I am trying to use the same .ism file in installshield 2013 premier trial version. I could generate .exe not the .msi file while clicking "Buils MSI" option. What settings is required in installshield to get .msi file instead of .exe file?