In order to include data from Bitbucket Data Center instances, you need to configure an application link between Confluence and Bitbucket Data Center.

This will then allow you to select the configured Bitbucket connection within the different macros provided by Include Bitbucket for Confluence Data Center.

To access data included via the application link, users will need to authenticate against the Bitbucket Data Center instance. You can find a recap of how user authentication is handled here.