To find this go to Central Admin and navigate to Upgrade and Migration | Click on Convert Farm License Type under Upgrade and Patch Management. You will see installed license type next to Current License ( It should say SharePoint Server with <Standard Or Enterprise> Client Access License)
You can convert the License by entering Product key printed on your Client Access License Agreement.
Or Upgrade and Patch Management | Enable Enterprise Features
Note - Once you have upgraded to Enterprise, you cannot switch back to use only the Standard features.