No window to enter code

Hi there. Just starting out and I’m possibly doing something wrong, but I’m just not able to enter my code anywhere. Including a screenshot. I have an instruction window, a preview window, and a window that says test output here, however, I can’t actually enter text in that window. Am I missing something? I’m on Chrome and I tried Safari and same issue. Help?

You should be able to type in the box which I have highlighted below.

Thanks so much! That was not very intuitive. I was imaging a larger window in which to work , but I guess this is fine for line by line.

The ‘typing window’ is sometimes considerably larger, once you are dealing with larger blocks of code… it just tries to keep things really simple to start with.