Random key generation with one time login

How can I make a C# project to login into the program through a one-time key, that is, every time you want to access the form2, you have to click on the (Get key) button that will take you to shortlink website (shrinkearn) To show you some ads then show you the key that you can login through which changes in Every time you want to log in to the form 2

Video explaining the idea:
RANDOM KEY GEN WITH ONE TIME LOGIN & EARNING FROM ADS