You can also take a look at the Licensing Usage report: Settings > Licensing, click the Usage Report button. On the Usage Report, click the Previous 30 days tab, and change the Split By dropdown to Index.
That role/permission is required to get to that information. You will have to speak with your Splunk administrator about getting access. If you want to just know how much you are using of the Splunk License, that is something that your Splunk Admin can set up so that you can see it. There are a couple of ways that I know of, and I created a summary index for my users to run the search from to see what their usage was, since they were not allowed access to that data directly.