The easiest method is to create a global variable vScore and a Sprite Font object, say ScoreText.
After you change vScore, use this action to update your sprite font text:
ScoreText -> Set Text to vScore
or
ScoreText -> Set Text to "Your score: " & vScore
With Sprite Font you can make your text as big as you want. And if it's not enough, you can further increase it with Scale