Window_Alert

function Window_Alert() {
    this.initialize.apply(this, arguments);
}

Window_Alert.prototype = Object.create(Window_Base.prototype);
Window_Alert.prototype.constructor = Window_Alert;

Window_Alert.prototype.initialize = function(x, y) {
    var width = Math.floor(Graphics.boxWidth * 0.263);
    var height = Math.floor(Graphics.boxHeight / 3.69);
    Window_Base.prototype.initialize.call(this, x, y, width, height);
    this.refresh();
};

Window_Alert.prototype.windowWidth = function() {
    return Math.floor(Graphics.boxWidth * 0.263);
};

Window_Alert.prototype.windowHeight = function() {
    return Math.floor(Graphics.boxHeight / 3.69);;
};

Window_Alert.prototype.refresh = function() {
        this.contents.clear();

        if(!this._windowAlertSprite) {
            this._windowAlertSprite = new Sprite_Base();
            this._windowAlertSprite.bitmap = ImageManager.loadPicture("kevinicon");
        }

        this._windowAlertSprite.x = (0.5 * this.windowWidth()) - (0.5 * this._windowAlertSprite.width);
        this.addChild(this._windowAlertSprite);

        var width = this.contents.width - this.standardPadding() * 2;
        var height = this.contents.height - this.standardPadding() * 2;
        this.contents.drawText("ALERTS", 0, 0, width, height, "center");
};

Scene_Menu.prototype.createAlertWindow = function() {
    this._alertWindow = new Window_Alert(0, 0);
    this._alertWindow.y = Graphics.boxHeight - this._alertWindow.height;
    this.addWindow(this._alertWindow);
};

//not sure where you're trying to create the window so I've put it in here...
var sceneMenuCreate = Scene_Menu.prototype.create;
Scene_Menu.prototype.create = function() {
    sceneMenuCreate.call(this);
    this.createAlertWindow();
};