Changing your database table prefix of an established from the original wp can be carried out by following the tutorial here: http://www.wpbeginner.com/wp-tutorials/how-to-change-the-wordpress-database-prefix-to-improve-security/
Changing the username of the administrator from the admin default is part of good security housekeeping by the site administrator, alongside other hardening WordPress steps: http://codex.wordpress.org/Hardening_WordPress
Wordfence has options to hide your WordPress version, block or throttle login attempts through the firewall.
As far as hiding your login/admin folders by renaming them, security through obscurity is considered questionable.
You are better off using two factor authentication (offered by WordFence premium), or restricting access by IP address.