How do I Use Google Licensing Service in Unity 5.0 or above?

Hello Comm-Unity, I am trying to publish my game, but I have one more thing to finish doing. As my app is going to cost money, I apparently need to use the Google Play License Base64-encoded RSA public key to verify that the app has been purchased by the user. So my question is: if I do indeed need to use Google Licensing, tell me if I'm wrong there, how do I go about putting the key into my game? Thank you for any help. - tiger27