In this application you can register a new contact, you have to click on the blue button below on the main page, and in the list where you have all your contacts, you can change, delete, order and call, when clicking on one of the contacts, they will appear the three buttons.

The first is to be able to call your contact, the second is to edit and the third is to delete. At the top of the app, there in the upper right corner, it contains three dots, they are to be able to sort your contacts alphabetically.