Prerequisites
Only JIRA Administrators and JIRA System Administrators can access the License Monitoring menu.
To open the License Optimizer menu:
Choose Jira Settings→ Applications.
Locate License Manager section and select the License Optimizer menu.
How License Optimizer works
License Optimizer adds and removes users from the group providing application access based on their activity in Jira. If users are not actively using the app, they are removed from the group and once they get active again are added to it.
For more detailed explanation, see here: How it works