how to get posts of a specific Blog Category

Dear All

I want on my page to echo only the particular category of posts, how do I do this, I assume this is the bit of code to amend to get the specific category …. but not sure how to do this – can anyone help?

<?php $query = new WP_Query( array( ‘posts_per_page’ =>’3′ ) );
if ($query->have_posts()) : while ($query->have_posts()) : $query->the_post(); ?>