Create your MailChip account here https://login.mailchimp.com/signup?pid=GAW
Once you have confirmed and activated your account you will need to click on the API keys link to create your API keys.
Please click on the Create API button and MailChimp will create an API key automatically.
Finding the API Key
The following screen displays all the API keys you’ve created. The following API keys provide full access to your MailChimp account, which is needed in order to integrate it with Booking Ultra Pro Plugin.
Creating a List
Just set a List name and fill out all the required fields, then submit the form.
Once you have created your List you will need to use the List ID to integrated it with the plugin. Just click on your List and you will be taken to the List’s dashboard.
Click on Settings – List name link and you will see the List ID at the right side of your screen.
Using the List ID & API Key on The Plugin
Login to your WP Dashboard then click on Booking Ultra Pro – Settings – Newsletter and activate MailChimp.
Scroll down and you will see the following screen:
Just fill out with the API key and Client ID obtained on your MailChimp account.