Public variables

Can we change public or private variables.

package pGame.data
{
    import flash.utils.*;

    public class GameData extends Object
    {
        private var _timer:Timer;
        private var _scores:Array;
        public var currentLevel:Number = 1;
        public var totalOpenedLevels:Number = 1;
        public var levelData:Array;
If so then pls tell me how it can be done.

Yes.  Read the Tutorials and FAQs