Photo Gallery help!

Total noob here that’s building a Flash site and having trouble with finishing my photo gallery. I’ve followed several tutorials online (including the one on this site) and have been successful except my pictures are appearing in the lower right hand corner of the screen; off the page. AND the pictures are aligned to the left, not centered.
Could anyone help me get the pictures to appear where they belong, and center the alignment so that horizontal and vertical pictures fit in the box?

Here’s my actionscript ( the last 2 lines for alignment I found on this forum. got the y axis aligned, but I can’t get it to slide over left no matter how many times I change the numbers:

function loadXML(loaded) {

if (loaded) {

xmlNode = this.firstChild;
image = [];
description = [];
total = xmlNode.childNodes.length;
for (i=0; i<total; i++) {

image* = xmlNode.childNodes*.childNodes[0].firstChild.nodeValue;
description* = xmlNode.childNodes*.childNodes[1].firstChild.nodeValue;

}
firstImage();

} else {

content = “file not loaded!”;

}

}
xmlData = new XML();
xmlData.ignoreWhite = true;
xmlData.onLoad = loadXML;
xmlData.load(“images.xml”);
/////////////////////////////////////
listen = new Object();
listen.onKeyDown = function() {

if (Key.getCode() == Key.LEFT) {

prevImage();

} else if (Key.getCode() == Key.RIGHT) {

nextImage();

}

};
Key.addListener(listen);
previous_btn.onRelease = function() {

prevImage();

};
next_btn.onRelease = function() {

nextImage();

};
/////////////////////////////////////
p = 0;
this.onEnterFrame = function() {

filesize = picture.getBytesTotal();
loaded = picture.getBytesLoaded();
preloader._visible = true;
if (loaded != filesize) {

preloader.preload_bar._xscale = 100*loaded/filesize;

} else {

preloader._visible = false;
if (picture._alpha<100) {

picture._alpha += 10;

}

}

};
function nextImage() {

if (p<(total-1)) {

p++;
if (loaded == filesize) {

picture._alpha = 0;
picture.loadMovie(image[p], 1);
desc_txt.text = description[p];
picture_num();

}

}

}
function prevImage() {

if (p>0) {

p–;
picture._alpha = 0;
picture.loadMovie(image[p], 1);
desc_txt.text = description[p];
picture_num();

}

}
function firstImage() {

if (loaded == filesize) {

picture._alpha = 0;
picture.loadMovie(image[0], 1);
desc_txt.text = description[0];
picture_num();

}

}
function picture_num() {

current_pos = p+1;
pos_txt.text = current_pos+" / "+total;

}
picture._x = 100 - (picture_width/2)
picture._y = 320 - (picture._height/2)