H1 in website

F.e. if you like to replace all h2 headings in the slider with h1 – put this into your child-theme functions.php

function replace_tags_with_tags(){
?>
<script>
  (function($) {       
      function replaceElementTag(targetSelector, newTagString) {
        $(targetSelector).each(function(){
          var newElem = $(newTagString, {html: $(this).html()});
          $.each(this.attributes, function() {
            newElem.attr(this.name, this.value);
          });
          $(this).replaceWith(newElem);
        });
      }
      replaceElementTag('.avia-slideshow h2', '<h1></h1>'); 
  }(jQuery)); 
</script>
<?php
}
add_action('wp_footer', 'replace_tags_with_tags');

if you just want this only on that page set an if-clause:

function replace_tags_with_tags(){
if(is_page(504)){
?>
<script>
  (function($) {       
      function replaceElementTag(targetSelector, newTagString) {
        $(targetSelector).each(function(){
          var newElem = $(newTagString, {html: $(this).html()});
          $.each(this.attributes, function() {
            newElem.attr(this.name, this.value);
          });
          $(this).replaceWith(newElem);
        });
      }
      replaceElementTag('.avia-slideshow h2', '<h1></h1>');
  }(jQuery)); 
</script>
<?php
}
}
add_action('wp_footer', 'replace_tags_with_tags');