Welcome to the forums. You have to have two things to connect to a PC and do something other than charge. Developer options have to be enabled on the phone/device and you have to have the correct USB drivers for the phone/device installed on the PC. You get the USB drivers from Samsung's website, not sure how to enable developer on the S4. Will ask that thread be moved to the S4 forum.
If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See
this link for instructions on how to join Android Central.