Creating a template thas shows post from a specify category

Replace this:

<?php if(have_posts()) : while(have_posts()) : the_post(); ?>

with this:

<?php $numposts = get_option('posts_per_page'); ?>
<?php $wp_query = new WP_Query('showposts='.$numposts.'&paged='.$paged); ?>
<?php if($wp_query->have_posts()) : while($wp_query->have_posts()) : $wp_query->the_post(); ?>

Leave everything else the same, and use the new WP_Query(...) object to filter by category (along with the showposts and paged options).

Thanks for the fast reply I will try it right away ??

hmmm it doesnt work

<?php get_header(); ?>

<?php $numposts = get_option('posts_per_page'); ?>
<?php $wp_query = new WP_Query('showposts=3'.$numposts.'&paged='.$paged); ?>
<?php if($wp_query->have_posts()) : while($wp_query->have_posts()) : $wp_query->the_post(); ?>

		<div class="post" id="post-<?php the_ID(); ?>">
			<div class="post-header">
        <div class="date"> <?php the_time('M j') ?> <span><?php the_time('y') ?></span></div>
				<h2><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
        <div class="author">by <?php the_author() ?></div>
      </div><!--end post header-->
			<div class="entry clear">
				<?php the_content('read more...'); ?>
        <?php edit_post_link('Edit This','<p>','</p>'); ?>
			</div><!--end entry-->
      <div class="post-footer">
        <div class="comments"><?php comments_popup_link('Leave a comment', '1 Comment', '% Comments'); ?></div>
      </div><!--end post footer-->
		</div><!--end post-->
		<?php endwhile; /* rewind or continue if all posts have been fetched */ ?>
		<div class="navigation index">
			<div class="alignleft"><?php next_posts_link('&laquo; Older Entries') ?></div>
			<div class="alignright"><?php previous_posts_link('Newer Entries &raquo;') ?></div>
		</div><!--end navigation-->
		<?php else : ?>
		<?php endif; ?>
	</div><!--end content-->
<?php get_sidebar(); ?>
<?php get_footer(); ?>

got it!!

<?php $wp_query = new wp_Query('cat=3&showposts='.$numposts.'&paged='.$paged); ?>

Once again thanks for the help!

Could one of you explain this in a detailed step by step for us total noobs?

Nnyan,
What exactly do you not understand?

I actually figured it out but thanks!