Ok this is from "Total Frontlines: Fuel of War's forum.
GOT IT!! heres what works:
there are three parts, i will walk you through them. note, this might look long, but if done right, takes under 5 minutes. the longest part is the loading times in-game.
PART 1 - revising the code:
1. locate the directory where you installed the game. navigate to "\GCGame\Config".
2. create a copy of the read-only file "DefaultInput.ini". place that copy in a folder for backup. the copy should be called "Copy of DefaultInput.ini".
3. open "DefaultInput.ini" with a text editor, probably windows notepad.
4. locate these three lines of code:
-Bindings=(Name="f",Command="Use"
-Bindings=(Name="f",Command="Use",DataboundVarName= "Use"
.Bindings=(Name="f",LookupName="UseActionKey"
(NOTE: yours might not say "f"
5. where mine says "f", and yours might say "E", change that letter to your preference.
PART 2 - saving the read-only file "DefaultInput.ini":
1. in order to save this file, you must save it with a different name. you will get these 2 warnings, in order: "do you want to save these changes?", "make sure the path and filename are correct". click ok to both.
2. save "DefaultInput.ini" as "aDefaultInput.ini".
3. you will notice that you now have both "DefaultInput.ini" and "aDefaultInput.ini". delete "DefaultInput.ini".
4. rename "aDefaultInput.ini" to "DefaultInput.ini"
5. pat yourself on the back, youve completed the hardest parts.
PART 3 - changing the keybindings in-game:
1. once in a game, go to the controls, and change any bindings that have been reset, which now conflict with your new action key.
in my case, this involved switching flares from "F" to something besides "F".