Categories Images- plugin instructions for a complete beginner

Hello,

This is my website: http://www.mighzal.com

I am a complete newbie to this.
I downloaded a “Categories Images” plugin in order to add images to categories. I installed and activated it, it lets me upload an image, but it doesn’t show up.
I realized the instructions also had:

Default usage:
use the following code in category or taxonomy template,put it in any <img /> tag :

<?php if (function_exists(‘z_taxonomy_image_url’)) echo z_taxonomy_image_url(); ?>
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<?php if (function_exists(‘z_taxonomy_image_url’)) echo z_taxonomy_image_url(); ?>

or simply:

<?php if (function_exists(‘z_taxonomy_image’)) z_taxonomy_image(); ?>
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<?php if (function_exists(‘z_taxonomy_image’)) z_taxonomy_image(); ?>

And it makes no sense to me. I don’t even know where to begin. Please assist