To open Test Explorer go to Test > Windows > Test Explorer:
The Test Explorer lists the Test Studio tests within the currently opened solution.
Test Explorer can list tests using five criteria: class, duration, outcome, traits, and project. Test Studio tests currently support sorting by Class, Duration, and Outcome.
To execute specific tests in the Test Explorer, use Run... and select a criterion.
Note: When executing tests from Test Explorer Test Studio test settings are not applied. To use the default Test Studio settings it will be necessary to add a project settings file and apply it for Test Explorer test execution as shown here.