Teachers can get the pro version for free. I do not want to add the code here because it is not for everyone - only teachers. I have e-mailed it to you but if you need it again just let me know and I can resend it. No problem. Students DO NOT need the free version, nor do I think they can get it. It is for teachers. But they (students) CAN use the regular version just fine.
Here is how to add it to Chrome.
You can also install it by using the waffle and searching for it. Same / same!
Here is the Video I made above from ScreenCastify.