Just create an instance of the class, and use your getter/setter methods like any other AS object. On your timeline, you would put the following:
code:
import score;
myScore:Score = new Score(0, "rookie" );
/* assuming you start with 0 points at a rank of rookie */
In your game, you would invoke the getter/setter methods.
code:
myScore.setpoints(20);
myScore.setrank("veteran");
At the end, let's say you have a screen with a textfield with an instance name of "displayScore_tf".
code:
displayScore_tf.text = myScore.getpoints();