Accordion feature

All the HTML code in the linked page is the html and class mandatory for creating bootstrap 3 accordeon. You have to cpoy/paste all of this code and put your custom fields inside this for the accordeon titles and content OR you could look at other extentions which provide simple bbcode to use inside your content depends your needs like this one.

Sorry, guys, but I can make very little sense out of the instructions you linked to. My understanding is that the template, like Joomla, uses bootstrap version 3. Can you please provide me with the html code I need to insert before and after the editor field and whatever code I need to add to the custom stylesheet? I am certain this information would be highly useful for many of your customers.

First you need to check the BootStrap version for your template and then you need to use the proposed html code in Bootstrap documentation to trigger accordion behaviour

So what exactly to I need do to make an editor field collapsible in EasyLayouts?

Hi Andrew,
with Easy Layouts you may add the html code for your wrappers and then trigger Bootstrap accordions via Data attributes:

https://getbootstrap.com/docs/3.3/javascript/#collapse-example-accordion