You need to define the SizingPeriod:DesignDay object from the Location and Climate Class (Third from top in the IDF editor). You can get this data from the ZIP file (if downloaded for weather file) from DOE website, named with an extension *.ddy. You can open this file from the IDF editor and find the necessary design day environment. Hope this helps.
I am getting error as Run design day simulations enabled but no design environment specified, I selected the appropriate weather file, what is design environment, where do give information regarding design environment