I am a amputee i have no left hand so i use razer naga molten mouse on my pc to game. Fallout 4 settings wont let me configure certain buttons.Says this button is reserved. Where is the file so i can just change it there or if anyone knows how to fix this problem i have razer synapse but it still wont bind.

In previous games, it was in the Prefs files I believe. Poke around in My Documents/My Games/Fallout 4 and look in the text files in there. If you mess the file up, just delete it and the game will create new ones. Just leave the ones in the root directory for the install of the game alone. Those are not replaced unless you Repair or Revalidate or Reinstall.

If your trying to remap the number pad keys, that may not be possible yet.