Basically, you need to place a GUI control in your scene to display the score value. Likely, you'll just need a
With that added. you can display a value in the control by setting the
text property of the label.
So, to put your value of your
fuel variable in the label, it'd look something like this:
$Label.text = str(fuel)
Depending on your game design (and scene layout), the trickier part might be in getting the value of
fuel available to the script that has access to the new
Label control. If the variable and the Label are part of the same scene, that's pretty easy.
Otherwise, you'll need to somehow pass the value from one place in your game to the other. That can be done via a
signal or by directly calling a function or setting a property in some other script. The details of that will vary based on your game.