I tried plugging it in on multiple usb ports, but it simply won't detect any imput, the "pairing" light on the bottom of the controller keeps flashing as if to indicate that it's waiting for confirmation. Do I need a bluetooth adapter?
Not sure if this is still an issue you're having since this post is old, but I wanted to throw my solution on here since your post came up when I was googling for answers myself.
Yes, it needs bluetooth. Press Windows and type "bluetooth" in, click on "Bluetooth and other devices settings" when it appears as a result. Now click "Add Bluetooth" and make your computer begin searching for a connection. Press and hold the little button to the left of your Afterglow's charging port for five seconds and then release. Your computer should recognize it, mine calls it "Lic Pro Controller".
For use with Steam, it should now work if you go to Settings > Controllers > Basic controller settings. You should see the controller recognized there. To start playing, enter Big Picture Mode on Steam and you should be able to navigate with the Afterglow.
If using a mod manager to launch games (ie. Skyrim), just make sure you have Big Picture Mode on and minimized when you launch from the mod manager and your controller should still be connected.