change input key from a script

If you're looking to change an input key at runtime, store the desired key in a static variable and reference it in your code:

 //GameSettings.cs
 public class GameSettings
 {
    public static GameSettings Settings;
 
    public KeyCode ToggleEngineKey = KeyCode.H;
 }
 
 
 //PlayerInput.cs
 public class PlayerInput
 {
    void Update()
    {
       if (PlayerControlled)
       {
          if (!SpawnMenu.IsPaused)
          {
             if (Input.GetKeyDown(GameSettings.Settings.ToggleEngineKey))
             { EnableEngines(!EngineRunning); }
          }
       }
    }
 }
 

Also, be more descriptive next time and show any relevant code you're working on.