Enabling .Net Framework 3.5 in Windows Server 2012 using Command prompt 

You need

1. Media of Windows Server 2012

insert your media in your dvd drive or mound it via iLo or pendrive

please not your drive letter which is assigned to that media

now open up your command prompt

press windows key and R key same time now run windows will appear  , now  type CMD  then press enter 

this will open your command prompt

now mound your drive letter

in this case my drive letter is  ”  D   “

so i need to type D: in the command prompt

now type following command

dism /online /enable-feature /featurename:NetFx3 /All /Source:d:/sources/sxs

Note*  in command line letter d may vary 



now wait for some time

done !

lets check on server manager