Okay you will hit a point where @ben sets the inputs up for an xbox 360 controller. Great if you have one!
I dont and discovered Unreal Editor will not see my standard windows USB controller.
So why is that?
Because Unreal editor uses an API called XInput and basically windows does not.
How do we fix it?
Well technically we dont. We have to use a third party piece of software called TocaEdit X360 Emulator.
IMPORTANT Put the x360ce app into the Engine/Binaries/Win64 folder
Run it from there
When its loaded up before changing any controls click the Game Settings tab.
Unreal Edtior is 64bit so we need a 64 bit dll.
I think the 1.3 is generic but you may have to test a few to get one that works for you.
Then set up your controller
Save and CLOSE the program
Run the editor and it should work!
I am doing this from memory as i did it for a game once but this should work as google agrees!
EDIT :- I actually failed to get this working so if you have any luck please let me know and how you did it, Thanks