When you signed up, you would have received an email titled New Account Information.
In there is a section titled Login Details from where you must extract a username and password.
Now ssh to your shared hosting, e.g.:
wget https://en-za.wordpress.org/wordpress-5.0-en_ZA.tar.gz or whatever the latest version of WordPress is at https://en-za.wordpress.org/download/
tar -xf wordpress…
move all the file in the /wordpress folder up one level so that they are in the root of ~/public_html
Now run WordPress from your website URL, and when asked to choose a database name, use the same name as your login name.