I leave you a bit of code which should help.
If you have doubts regarding the code, here is more info on setters and getters:
# with this setup, whenever you do self.labelText = "SOME_TEXT",
# your label will update with that text. It'll also work if you
# set the labelText var from some other object/script
var labelText = "" setget setLabelText
onready var label = $Label
func setLabelText(text):
labelText = text
label.text = text