After setting up your tasks it is possible to take a look at what the tester sees once he starts conducting your test.
On the bottom of the page you will find the grey "preview" button.
You will then be able to click through your tasks to check if everything looks as planned. There is an option on the top of the preview to see how test looks both in the desktop and mobile version.
Please note that the preview will not show the URL you input - the example site is a white window.