Stick JSON-LD code in a custom field called 'schema' and use the PHP snippet to insert into relevant page. PHP should go into header.php just before closing tag.
<script type="application/ld+json">
{ "@context" : "http://schema.org",
"@type" : "Organization",
"legalName" : "Elite SEM",
"url" : "http://elitesem.com/",
"contactPoint" : [{
"@type" : "ContactPoint",
"telephone" : "+1-646-350-2789",
"contactType" : "customer service"
}]
"logo" : "http://elitesem.com/wp-content/uploads/2014/03/Elite_SEM_Logo_2014.png",
"sameAs" : [ "http://www.facebook.com/EliteSEM",
"http://www.twitter.com/elitesem",
"http://plus.google.com/+Elitesem",
"https://www.youtube.com/user/EliteSEMInc",
"http://www.linkedin.com/company/elite-sem",
"https://www.wikidata.org/wiki/Q20736641"]
}
</script>
<?php
$schema = get_post_meta(get_the_ID(), 'schema', true);
if(!empty($schema)) {
echo $schema;
}
?>