How do I transfer files from my pc to my phone? Kies3 no longer supporting device.

[gammywoo]

My wife gave me her S4 after upgrading to an S6. When I tried to connect it to Kies3 so I could upload a video from my PC, which I've done for her many times before, it tells me to download Smart Switch. I downloaded Smart Switch to my desktop and it told me to upgrade my software, which I did. After an hour or so of waiting my phone looks lovely with its upgraded software, but when I connect it to Smart Switch the only option this damn package gives me is to back up or restore. There are no options for transferring files one at a time from PC to phone. Kies3 was so quick and easy to use, but now I can't do anything! Can someone please help? I'll bet it's something simple.