add offset to archive page

I am not sure what exactly you are trying to do. Here is an example using offset. For a category the first post is being displayed and that can have a unique HTML structure/layout.

Then the remaining posts are shown but the search omits the first results and it offset by one item. Does this make sense to you?

If you are looking for good video tutorials on learning how to develop themes have a look at this. There is also one on archives and custom queries, highly recommended.

<?php
    // Get first post from category
    $args = array(
        'category_name' => 'the_name_of_the_category',
        // Display only the first post on this category page
        'posts_per_page' => 1
    );
    $search = new WP_Query( $args );
        if($search->have_posts()) :
            while($search->have_posts()) : $search->the_post();
                post_class(); 
                the_content();
            endwhile;
        endif;
    wp_reset_postdata(); 

    // Get the ramaining posts but start at 2nd position
    $args = array(
        'category_name'  => 'the_name_of_the_category',
        'posts_per_page' => 5,
        // So here we start with the 2nd post in the search and not in the First
        // the offset in the arguments for this post query is one
        'offset'         => 1
    );
    $search = new WP_Query( $args );
        if($search->have_posts()) :
            while($search->have_posts()) : $search->the_post();
                post_class(); 
                the_content();
            endwhile;
        endif;
    wp_reset_postdata();
?>