Installing the Plugin is pretty much as with every other CakePHP Plugin.
Put the files in Plugin/Mailchimp, using Packagist/Composer:
composer require dereuromark/cakephp-mailchimp:1.0.*
which will add the following to your composer.json file:
"require": {
"dereuromark/cakephp-mailchimp": "1.0.*"
}
Details @ https://packagist.org/packages/dereuromark/cakephp-mailchimp
This will load the plugin (within your boostrap file):
Plugin::load('Mailchimp');or
Plugin::loadAll(...);