If you don't already have a CartStack account, sign up here 

Log into your CartStack account and copy your unique tracking code from the code page.  Your siteid is also included inside the tracking code. You will also need to copy the API Key. 

You will now need to login to your CoreCommerce admin area.
Go to Settings      > Plugin Apps      > CartStack  

Input the Site ID,  API key, and Tracking Code you obtained from your CartStack account > Save.
Finally, go back to your  CartStack code/setup page to finalize the setup.  Enter the thank you / confirmation page URL of your store and then click "Review my Integration".  (ex: https://yourstore.com/orderSubmitted.php)

 A CartStack team member will review your site and email the account holder when the integration has been reviewed.