How can i add multiple balls?

If you are adding them manually then just add them and then place their instance names in an array so that you can loop thru the array in your loop function.

var ballNum:int = 10;  // or whatever

var ballSpeedX:int = -9;

var ballSpeedY:int = -12;

var ball:Ball;  // create Ball class

var ballA:Arrray = [];

var i:int;

for(i=0;i<ballNum;i++){

ball=new Ball();

ball.speedX = ballSpeedX*Math.random();  // or whatever if you want them to have different speeds

ball.speedY = ballSpeedY*Math.random();

ball.x=?

ball.y=?

ballA.push(ball);

}

init();

function init():void

{

stage.addEventListener(Event.ENTER_FRAME, loop);

}

function loop(e:Event):void

{

for(i=0;i<ballA.length;i++){

ball=ballA;

ball.x += ballSpeedX;

ball.y += ballSpeedY;

if(ball.x <= ball.width/2){

ball.x = ball.width/2;

ball.speedX *= -1;

} else if(ball.x >= stage.stageWidth-ball.width/2){

ball.x = stage.stageWidth-ball.width/2;

ball.speedX *= -1;

}

if(ball.y <= ball.height/2){

ball.y = ball.height/2;

ball.speedY *= -1;

} else if(ball.y >= stage.stageHeight-ball.height/2){

ball.y = stage.stageHeight-ball.height/2;

ball.speedY *= -1;

}

if(ball.hitTestObject(wall.wallu) || ball.hitTestObject(wall.walld))

{

ball.speedY *= -1;

}

if(ball.hitTestObject(wall.walll) || ball.hitTestObject(wall.wallr))

{

ball.speedX *= -1;

}

}

}