Internationalizing my plugin

I’m gonna deploy my first plugin but the _e() and __() functions seem don’t work.

In my comments header:

Text Domain: add-to-post-footer
Domain Path: /languages

I created .po and .mo files with poedit and put them in /languages in my plugin. I translated to portuguese and named as ‘pt_BR.po/mo’. In my option page I have some texts as follows:

<?php echo __( 'With ', 'add-to-post-footer').ATPF_PLUGIN_NAME.__(' you can add some content at the final of all your posts without care about forget some of them, or the need to copy and paste boring proccess. Just go to Posts >> ', 'add-to-post-footer').ATPF_PLUGIN_NAME.__(', insert the content and save it. The proccess is the same to change the content. You just have to care about other stuff of your site/blog now', 'add-to-post-footer'); ?>

But when I put in my localhost wordpress installation, language brazilian portuguese, nothing happens (just the save button, because Save is already translated by default on WP)

What am I doing wrong?