Why I cannot type in the text editor of scratch files?

I've just installed PyCharm Professional Edition 2018.2.4 and have the latest version of Python (3.6.5) as my project interpreter. I've made a new project called "Hello World" and I can type in it.

But when I establish a new scratch file under the 'Scratches and Consoles', I can't type in any letter in the text editor of that scratch.py file. The text cursor appears but every time I hit a button it just makes a sound. How do I fix this?

BTW, I haven't purchased the licence yet. And I am installing your IDE on Windows 10.