Ahphabetical paginatin doesn't show on my page

May I have your website url?

yes, this is it https://cuidatufuturo.com/diccionario-financiero-2/

Can you please take a screenshot of plugin settings page from wp-admin?

In this llink you can find it

https://dl.dropboxusercontent.com/u/94568045/Screen%20Shot%202015-07-20%20at%205.11.39%20PM.png

Are you trying to display alphabets with a shortcode?
[ap_pagination]

Yes

If yes, then shortcode is only available in pro version. If you are fine with using it as Auto then try this one https://prntscr.com/7v2923

Still dosent work I use as auto but dosent show at the category selected

Please me your login credentials through my blog

Ok

Free plugin works with categories
https://cuidatufuturo.com/wp-admin/edit-tags.php?taxonomy=category

But you were trying it with a page
https://cuidatufuturo.com/diccionario-financiero-2/
its not a category but a page. For pages and other custom areas, you need pro version. Free version works with archives, taxonomies and default main query.

Here is a working example from your website
https://cuidatufuturo.com/category/audio-y-video/