[Plugin: WP-PageNavi] Pagination for Dummies, please?

I have read the instructions, and posts in forum, but I still don’t get it how to paginate.

1) I have installed “WP-PageNavi”.
2) I have put “<?php if(function_exists(‘wp_pagenavi’)) { wp_pagenavi(); } ?>” in footer.php.

But what do I do next?

For example, I have a post with the following content:

This goes to page 1
This goes to page 2
This goes to page 3

What kind of tags should be inserted in a post between these blocks of content for pagination to work?