Seems like you followed the example and fixed the error once, now you need to click on each of the errors and link each of the individual green 'Add" buttons to their respective actions and entities.
It looks like the 'Add' button you have selected currently is set to do 'nothing' as per the on-click action over in the right hand menu. To fix the error, you will need to link the 'Add' button to your Teacher_NewEdit page. Click the 'More' option in your button even menu. This will give you the dropdown for 'Action' where you can fill in the details like you have done in your other pages.
Good luck with the intro course.
Thanks Bob! Works now!
Seems like you did configure the selected Add button in your printscreen to create a teacher object. Maybe you have some simulair buttons on the same screen that needs to be set? Since all error are pointing to the same screen? Click the error to see which button gives the error.