[Plugin: Amazon Product In a Post Plugin] Inserting an item within a post

I don’t understand the instructions for how to insert this plug-in code into an existing post.

It says

= To Add a product Via Shortcode: =
* In the Content editor, add **[AMAZONPRODUCT=XXXXXXXXXX]** where XXXXXXXXXX is the Amazon ASIN/ISBN10 number.
* Update the Page/Post. You can add as many products this way as you like.

When I do this all I get is the phrase “**[AMAZONPRODUCT=XXXXXXXXXX]**” in the text of my post. Not what I intended.

What else am I not doing that I need to?

Thanks.

http://ww.wp.xz.cn/extend/plugins/amazon-product-in-a-post-plugin/