Right-click on the element whose class you want to find out and select Inspect in the context menu that appears:
Make sure you are in the Elements section.
The large canvas with the code on the right and the element on the left that you clicked on is highlighted in blue. You can select another element and also find out its class.
The class of the element is highlighted in the screenshot.
The class has the form .tn-elem__2068601511470210224069
