Registration plugin extended fields with a short code

Hello,
I would like to kindly ask a question about the adding of a short code (this one: [paky_regioneprovinciacomune]) into a registration/login plugin, possibly extending the Word Press native user management (but it’s ok olso a stand alone plugin).

The goal is to extend a registration form with the features delivered by the regioneprovinciacomune plugin.

As you probably have noticed, I’m a Word Press beginner, sorry if my question is a little bit naive.

Thank you in advance for your kindness.

GianMatteo