Refer this Official documentation.

https://confluence.atlassian.com/doc/registering-external-gadgets-204050482.html

On Jira, e.g. Search for Gadget ** Jenkins Project One Status **

Click Show XML link and copy link.

Go to Confluence administration > External Gadgets > Add New Gadget with above link.

That's it, now try using confluence macros with above Jenkins gadget names.