For Windows 10.
*First, you have to make sure to close the game before doing anything. And this one is not necessary but I recommend you to make a copy of the main folder as a backup. (As a precaution)*
Now, to apply the bugfix, you simply have to copy everything from the bugfix folder and paste in the main folder. A message will pop up, asking you if you want to "Replace the files in the destination", click onto it and wait for everything to be copied over to the main folder. And voilà, you are good to go. Hope this is helpful.