ProgressBar works by displaying a value, set by the
value property. All you need to do is increase that property's value each time the key is pressed.
Have you already created the scene? Do you already know how to detect input? Your question is not very specific so it's hard to know how much information you need.
If it's just a case of how to increase the bar's display,
$ProgressBar.value = 0
# Assuming you want "spacebar" to be the "interaction key"
$ProgressBar.value += 1 # or whatever amount you want