How can I display custom post types on a page?

Easy: modify the query… (and add some comment on top to make a template out of this…)

$query_default = new WP_Query( array(
     'orderby'      => 'menu_order'
    ,'order'        => 'ASC'
    ,'post_type'    => 'custompost' // THIS IS WHAT YOU'RE SEARCHING FOR
    ,'post_status'  => 'publish'
) );
    if ( $query_default->have_posts() ) :

        while ( $query_default->have_posts() ) : $query_default->the_post();

        endwhile;

    else : // else; no posts
        _e( 'Nothing published so far.', TEXTDOMAIN_CONSTANT );
    endif; // endif; have_posts();

    wp_reset_query();