Wordpress - Sort results by name & asc order on Archive.php

The easiest way to do this is to use a hook (the pre_get_posts hook) to change the order. But you should check that the query is one for which you do want to alter the order! (is_archive() or is_post_type_archive() should be sufficient.)

For instance, put the following in your theme's functions.php...

add_action( 'pre_get_posts', 'my_change_sort_order'); 
    function my_change_sort_order($query){
        if(is_archive()):
         //If you wanted it for the archive of a custom post type use: is_post_type_archive( $post_type )
           //Set the order ASC or DESC
           $query->set( 'order', 'ASC' );
           //Set the orderby
           $query->set( 'orderby', 'title' );
        endif;    
    };