I managed to solve this and access the JSON data using a foreach
loop:
$json = lusso_posts();
#var_dump( $json );
#die();
foreach( $json as $post ) {
$titles = $post->title;
$images = $post->featured_image->guid;
?>
<div class="lusso-posts">
<div class="image-container"><img src="https://wordpress.stackexchange.com/questions/210472/<?php echo $images; ?>" /> </div>
<h4><?php echo $titles; ?></h4>
</div>
<?php
}