Google has certain defaults in place for two factor authentication, so it may not immediately show you the option for entering a code from Google Authenticator. If your screen looks something like the first picture (notice it is asking me to go into a Youtube App), find the words "Try Another Way" somewhere toward the bottom and click on them. This will take you to the option to select getting a code from the Google Authenticator App.
If you are having trouble entering a code for Groupwise Messenger...watch this:
If you need to remove Groupwise Authentication and set it up again...watch this: