A guide on how to use the keybind menu.
Guide to Using the Keybind Menu
In the key binding menu if you want to, for example, bind move forward from W to E you first bind move forward to W (which unbinds it) and then you bind it to E.
Alternatively you could just edit this file:
- c:\users\<user name goes here>\Saved Games\Nightdive Studios\DOOM 64\kexengine.cfg