WordPress - Agregar código Wordpress

<style>

.grid {

    position: absolute;

    right: 0;

    width: 80vw;

}

.section {

    min-height: 200vh;

}

</style>

<?php

$page = 4;

$pages = 10;

$paged = 1;

if (isset($_POST['page'])){

$paged = $_POST['page'];

}

echo '<script>

     function siguiente() {

       document.getElementById("page").value = parseInt(document.getElementById("page").value) + 1

       document.form1.submit();

     }

     function anterior() {

       document.getElementById("page").value = parseInt(document.getElementById("page").value) - 1

       document.form1.submit();

     }

    </script>';

//$paged = (get_query_var('paged')) ? get_query_var('paged') : 1; 

query_posts("category_name=Productos&paged=".$paged."");

    /* Start the Loop */

    while ( have_posts() ) : the_post();

        $post = get_post();

        $post_id = $post->ID;

        if(get_the_category( $post_id )[0]->name == "Productos"){

        ?>

    <div class="post" style="line-height:100%;" >

        <p class="descripcionP" style="line-height:1;"><?php the_title(); ?></p><br>

        <img src="<?php the_post_thumbnail('full'); ?>

        <br>

        <button class="detallesP" type="button" style="height:25px;border-radius:2px" onclick="location.href='<?php echo get_permalink($post_id); ?>'">Ver detalles</button>

    </div>

<?php

    }

    endwhile; // End of the loop.

//<div style="cursor:pointer" onclick="enviar()"><a href="">SIGUIENTE »</a></div>

// if ($page == 1) echo ""; else echo "<li><a href='?p=$page'>« PREVIO</li></a>"; 

// if ($page == $pages) echo ""; 

// else echo "<li><a href='?page=3'>SIGUIENTE »</li></a>"; 

  echo '<form id="form1" method="post" style="position:absolute;top: 74%;margin-left: 15%">

    <input type="hidden" name="page" id="page" value="'.$paged.'" />

    <input type="submit" class="btn btn-success" value="Anterior" onclick="anterior()">

    <input type="submit" class="btn btn-success" value="Siguiente" onclick="siguiente()">    

    </form>';

?>