shortcode for displaying CustomPress

I don't understand how to display the custom post I created. The instructions don't make any sense to me, unfortunately (

"You can use these Embed Codes 2 ways:

Simply enter the shortcode created on any page or post, directly in the WordPress editor, or
You can embed the php embed code in the page template so that you don’t have to manually add the shortcode to each post. To do this follow the instructions below:"

Well, I want to use the shortcode.

I made custom post "custom_post" and custom category "custom_post_category."

Then I create a new post in the new Custom Post area, and created a new "Custom Category" to give it.

Then I copied the shortcode to a post:

[tax id="custom_post_category" before="your text before: " separator=", " after=" your text after"]

When I preview the page I get nothing displayed

So I tried:

[tax id="custom-category" before="your text before: " separator=", " after=" your text after"]

That brings "Invalid Taxonomy name in shortcode"

So, how do I get the new Custom Post post I made to display? Also, what are "before," "separator," and "after" for? None of that seems to be explained in the instructions I linked to above. In less I'm being incredibly dense, which is very likely. Sorry!