How can a project administrator control who has access to a JIRA project?

A project administrator can control who has access to a JIRA project by configuring user permissions. This involves defining roles and permissions for different user groups or individuals within the project. The administrator can specify whether users have read-only access, can edit issues, can administer the project, or have other custom permissions. By managing these permissions, the administrator ensures that only authorized users can interact with the project's data and functionalities.