Hello blob, if you got the word “tags” it means it’s ready to display them, all you have to do is write the tags in the post editor once you have wrote the post. The cloud is modificable and stylable, I think it displays about 40 tags by default.
If you have some problem you could write it in the sidebar’s template directly, like this:
<?php wp_tag_cloud(''); ?>
,under the other calls usually in a sidebar : calendar, categories, etc.