Lets say you have five test cases and you want to execute all five test cases in different browser instance. When we say different browser instance it means open browser, execute first test case and close the browser. This pattern should be followed for all the selected test cases to execute.
In order to accomplish this, go to BeatBlip agent > Settings > Create new session for each iteration and check this checkbox.
This will execute all selected test cases in different browser instance.
In order to make this setting as default you have to save this selection on the web application in your project.
Open BeatBlip web application, select your project and go to Settings > Project Settings > Test Environment > test_adapter_reset_per_iteration and mark this setting as yes.