Update README with better instructions.

README.md

@@ -2,4 +2,13 @@
 Fully re-mappable DInput GCN controller to Luma InputRedirect.
 Also supports keyboard inputs.
 
-Technically supports any DInput device (i.e. Windows joystick), or any device that PyGame natively supports, but is currently mapped for a Gamecube Controller Adapter
+Technically supports any DInput device (i.e. Windows joystick), or any device that PyGame natively supports, but is currently mapped for a Gamecube Controller via a USB adapter.
+
+To remap controls, just edit the buttonMappings array or KBDButtons class in gamepad.py (or two.py if using multiple systems). 
+
+The buttonMappings array is just every button on your controller in order from 0, so if you want button 0 on your controller to be button A on the 3DS, put `HIDButtons.A` first in the list. 
+Likewise, if you want button 3 to be A, put `HIDButtons.A` as the 3rd item in the list. 
+If you want a high-numbered button (like the XBox 360 Guide button, #15 on some OSes) to be bound to a 3DS button, just add empty list entries (zero) in between the last button map and the one you want. 
+
+To remap joystick axes (if your controller for some reason uses different ones) find `pygame.JOYAXISMOTION` with ctrl+f and change the joystick axis indices (`event.axis == 0` etc). 
+~~(I will fix that later)~~