The dongle is bluetooth and DS3/PS3 controllers use bluetooth? If so run whatever the bluetooth thingy is in Windows and make sure they are paired up (I don't really know how it work on the controller but pressing the home/share/PS/whatever button and maybe holding it or something such while searching for bluetooth devices in Windows.)
It'll be way easier to remember those on a controller (even a different one) than mouse and keyboard. I hope someone can help with this! I really need it so I can finally play Dark Souls 2, since the SotFS version doesn't allow for texture editing, which means I'm stuck with the default Xbox button prompts. That same port is no longer making that happen. My previous attempt at this, several days ago, one port I tried the dongle in made the controller vibrate endlessly after I'd installed the suggested things. The Windows thing for detecting and calibrating controllers isn't seeing it either, with the controller itself also plugged into the computer or not. But when I run Better DS3 (which is the other place I guess I could turn to for support), it doesn't show any connected controllers. At this point, whether some of the things I've tried have stuck or not, I plug the dongle in, Windows (8.1) makes the appropriate noise, Device Manager refreshes and shows "libusbK USB Devices" and under that "Wireless Controller for PS3". I'm attempting to get this Afterglow wireless PS3 controller that I've never used but have had for a while now working, and I'm having a LOT of trouble. If this is the incorrect section for this question, I apologize.