To access your Custom Fields from your WordPress template files:
<?php echo get_post_meta(get_the_ID(),"thecustomfieldname",true);?>
And showing code in your WordPress blog post like above ...
Open with <pre><code>.
Then use & l t ; and & g t ; for the < and > characters in your code.
Then close with </pre></code>
The "Keeping It Simple..." series is short notes on how to do things on WordPress, writing PHP, using social media ... everything and anything... when you just want a quick reminder without all the explanations