Search in archive-{post-type}.php

Hi to everyone. I’m trying adding form at the top of my archive page. Also looking for custom field search included in the form? Any ideas how? :/ Thank you.

Edit: I’ll begin will building my custom search in functions.php -> Next (should i declare the searchform.php somewhere, or can just add <?php get_search_form( ‘my_custom_search_form’ ); onto archive-{post-type}.php surrounded by styling divs?) Else is the question with custom fields, but thats, at least for now, another dimension.

Edit 2: I forgot to say, that this searchform is gonna working only for that specific custom post type.