You add it in just as you would any other html. Lace it into your templates and chunk as and when applicable.
So for example if you had an organisation you could optionally put this at the top of your HTML (either in a template or chunk).
<html lang="en-GB" dir="LTR" itemscope itemtype="http://schema.org/Organization">
Then proceed to also add in a bunch of meta data like so:
<!-- SEO Microdata (Schema.org Variant) - Google, Bing, Yahoo -->
<meta content="[[++company-name]]" itemprop="description">
<meta content="[[++company-name]]" itemprop="name">
<meta content="http://www.[[++company-url]]" itemprop="url">
<meta content="http://www.[[++company-url]]/meta_thumbnail.png" itemprop="image">
<meta content="info@[[++company-url]]" itemprop="email">
<meta content="" name="author">
<meta content="[[*description]]" name="description">
<meta content="" name="google-site-verification">
<meta content="[[++company-name]]" name="companyright">
You could also setup some system settings or template variables and assign those variables to templates to have more control over the microdata of each page - much like the description in the example above would be using the resources individual description.
Or if you had some products and you were using something like getResources or pdoResources to pull in a bunch of product resources then you could use a chunk laced with schema microdata to do so.
<div itemscope itemtype="http://schema.org/ItemList">
<link itemprop="url" href="http://multivarki.ru?filters%5Bprice%5D%5BLTE%5D=39600" />
<span itemprop="numberOfItems">315</span>
<div itemprop="itemListElement" itemscope itemtype="http://schema.org/Product">
<img alt="Photo of product" itemprop="image"
src="http://img01.multivarki.ru.ru/c9/f1/a5fe6642-18d0-47ad-b038-6fca20f1c923.jpeg" />
<a itemprop="url" href="http://multivarki.ru/brand_502/">
<span itemprop="name">BRAND 502</span>
</a>
<div itemprop="offers" itemscope itemtype="http://schema.org/Offer">
<span itemprop="price">4399 р.</span>
</div>...
<div itemprop="itemListElement" itemtype="http://schema.org/Product">
...
</div>
</div>
</div>
