I can't activiate the Show Checkness box

I’ve been trying to do this for more than an hour and I can’t find how to activiate the Show Checkness box such as in Slides 10, 13 and 17.

Thank you for anyone’s help.

It will require some coding in the CL. </> for the components. Also look at the teacher comments I put on those 3 screens.
Here is an example using your activity