How to add structured data

Dear Community,

I’d like to add structured data (like schema.org) to our blog articles. Therefore I created a new component and added the code below:

<script type="application/ld+json">
{
  "@context": "http://schema.org",
  "@type": "BlogPosting",
  "headline": "${page.context.thread.topicMessage.subject}",

  "image": {
    "@type": "ImageObject",
    "url": "",
    "height": "",
    "width": ""
}	
  "datePublished": "${page.context.thread.topicMessage.postDate?datetime}",  
  "author": {
    "@type": "Person",
    "name": "${page.context.thread.topicMessage.author.login}"
  }
}
</script>

It’s fine so far, but how can I add more info like image, heigh an width?

Are there any other recommendations how to add structured data?

Thank you, best regards,

clemensw