thirst will automatically show you your course in desktop view by default. Because all thirst components are responsive, your course will adapt to whatever sized screen your learner is using.
To test how your desktop course responds to different sized monitors and screens, you can change the size of your browser and watch how your thirst course responds.
To see what your course will look like on a mobile, simple toggle to 'mobile view' which is in the black bar at the bottom of the screen.
You can continue to edit your course in mobile view if you prefer.
To find out more about editor view and learner view ready this article: