I am trying to get a mobile device to send a push notification to another following a course.
In the image you can see that in the course I am following the cloud messaging server key appears

But when I go to my project and look for the server key it does not appear as seen in the second image

The main code I have made is the following (image 3)

On the line with red would be the server key that I want to obtain. My question is how do I obtain this key?

Any help is useful, thank you.