The Newsletter module allows you to create multiple contact forms you can use as newsletter system of your shop.
The module can be activated or deactivated at any time from the correlated Modules section.
If the module has been activated, in the sideber of your site you will find the Newsletter custom post type you can use to configure the contact forms for your newsletters.
2. Create a Newsletter Form
Click on "Newsletter Form > Add New Form":
You can create three different kinds of newsletter form using Form integration preset field.
2.1 Custom Form
Using this type of newsletter, you can send form information to a specific URL (trough action field). Ex. http://www.mywebsite.com/newsletter-subscribe.php
Read the documentation of MadMimi to find information and discover how to use MadMimi API key.
Here you can find the documentation of MailChimp and read how to use MailChimp API keys.
After a newsletter form is created, it will be shown in newsletter form list and there you can see the shortcode column as showed below: