Configure a JIRA Server
Steps
Define a JIRA instance in the JIRA administration, giving it the id page authors pass to the JIRA Macros and the Scripting API, and the credentials the wiki reads non-public issues with.
- Log in as a user having administration rights on the wiki.
- Go to the wiki administration and click "JIRA" to open the "JIRA Instance Definitions" section.

- Click "Add JIRA instance".
- Fill the "Id" field with the name page authors will use to designate this instance, for example xwikiorg.
- Fill the "JIRA URL" field with the base URL of the instance.
- Select "No authentication" in the "Authentication type" field to read only public issues, or "Basic auth" to read issues as a given JIRA account.
- Fill the "Username" and "Password" fields under "Authentication system configuration" when you selected "Basic auth". On Jira Cloud, enter the account email address as the username and an API token as the password. Data Center personal access tokens cannot be used: they require bearer authentication, which the extension does not send.
- Click "Save".
- Insert a jira Macro in a page with its id parameter set to the id you chose. The issues of that instance are displayed.

FAQ
Which URL do I enter?
The base URL of the instance, the one the browser shows before the path, without a trailing path segment.
Should I use a password or a token, and is it safe?
Use a token whenever the instance offers them, since it can be revoked on its own, and reach the instance over HTTPS: Basic authentication sends the credentials merely encoded, not encrypted.
Can I define several instances?
Yes, as many as needed; each gets its own id, and "Add JIRA instance" adds another entry.
How do I remove an instance?
Click "Delete" on its entry, then "Save". Pages whose Macros use that id will report an error afterwards.
Why do I still get an error after configuring the credentials?
Most likely the account cannot read one of the issues being requested, or the query itself is invalid. See JIRA Connection Errors.
Do the definitions apply to the whole farm?
No. They apply to the wiki they are created in, so a subwiki that needs the same instance defines it again.
Which JIRA versions can the wiki reach?
Only those listed on JIRA administration.