You cannot get to the “backend” at wordpress.com.
Have you gotten a web host, registered a domain name, and installed the software from here at www.ads-software.com? All of that has to be done and set up first. You will also have to pick out a theme and upload it to your new blog if you do not want to use one of the basic ones included with the www.ads-software.com software.
You then have to export your posts, pages, categories and such under manage > exports in your dashboard at wordpress.com, and then import it into your new self-hosted blog by going to manage > import in your new blog dashboard.
Links will have to be imported separately from your new blog dashboard by going to blogroll > import and entering https://sspaint.wordpress.com/wp-links-opml.php
This FAQ at wordpress.com will give you some more information: https://faq.wordpress.com/2007/02/23/how-do-i-move-between-blogs-2/