How to setup phpMyAdmin to use cookie authentication

This guide will describe how to setup phpMyAdmin to use a cookie/session based login system.
The advantage of the cookie based logins is that you can get an exact mysql error as to why you can't login (if you can't login).

Edit:
/var/www/html/phpMyAdmin/config.inc.php

Change:

$cfg['blowfish_secret'] = '';

to

$cfg['blowfish_secret'] = 'anyrandomtextyouwant';

and change:

$cfg['Servers'][$i]['auth_type']     = 'http';    // Authentication method (config, http or cookie based)?

to:

$cfg['Servers'][$i]['auth_type']     = 'cookie';    // Authentication method (config, http or cookie based)?

Close all browsers and try to connect again.

NOTE

You may want to instead simply enable the one-click single-signon for phpMyAdmin which enables cookies by default:
One-Click login to RoundCube and phpMyAdmin