Hello baggio16,
You probably want to create a custom template.
1. Create a new file and name it "template-members.php" and place it in your theme folder.
2. Copy and paste the contents of "/wp-content/themes/infocus/archive.php" into your new file.
3. At the very top of your new file change it so it looks like this,
<?php
/*
Template Name: Members Page
*/
get_header();
require(WEBTREATS_INCLUDES . "/var.php");
4. Find line 99 which should look like this,
query_posts($query_string . '&cat='.$exclude_blog_cats); ?>
And change it like this,
query_posts($query_string . '&category_name=members'); ?>
And change "members" with the slug of your category.
5. Create a new page in Wordpress and select your new template.
Let us know if this helps baggio16.