Copy system/application/libraries/Dynect_API.php to your application/libraries folder
Review the sample code in system/application/controllers/welcome.php

Config

Ideally, there would be a config file in system/application/config but I haven't gotten it to work properly yet.

In the system/application/libraries/Dynect_API.php file, edit these lines as necessary based on info provided by Dynect:

var $user_name = '';
var $customer_name = '';
var $password = '';

Usage

First, load the library and instantiate the class.

$this->load->library('Dynect_API');
$dyn = new Dynect_API();

Then, login. Make sure to logout at the end.

$dyn->login();
// do things
$dyn->logout();

What you do is up to you. Here's what I've written so far:

print_r($dyn->get_all_records('foobo.com','test.foobo.com'));
print_r($dyn->get_zones());
print_r($dyn->create_zone("feebeetest1.com", "admin@feebeetest1.com", 3600));
print_r($dyn->publish_zone("feebeetest1.com"));
print_r($dyn->delete_zone("feebeetest1.com"));
print_r($dyn->get_records('A','foobo.com','test.foobo.com'));
print_r($dyn->create_record('A', 'feebeetest1.com', 'test.feebeetest1.com', array('address' => '127.0.0.1')));
print_r($dyn->delete_records('A', 'foobo.com', 'test.foobo.com'));