how to change wp template size

hello
i m student of word press and recently i have started to make e commerce web site with bilata wordpress theme. myy testing URL name is http://www.test.atqfashion.com
firstly i am facing problem to maintain its theme background. if you see its not accurate on the screen,from left and right. kindly help me in detail that how can i maintain its sizing?from that its shows perfect on the screen. my theme style sheet shows only these codes :
/*
Theme Name: ATQ FASHION
Theme URI : http://invisageint.com/
Description:
Author: akhtar husssain
Author URI: http://atqfashion.com.com/
Version: 1.1
*/
@import url(‘css/style.css’);