Oh, and you will need to reply to the email from Patti.
Just to make sure it is clear, you wont get an email from Patti, you will get a message in fibs, asking you to email her at email@example.com
That will allow her to keep your email address, should there be any problems with your account later [lost passwords, etc].
Have you managed to actually log into fibs, but cant play, or have you not got that far yet?
If you have not logged in at all - follow the instructions as socksey told you, watch for the message and reply to it via email.
If you have logged in before, you will have missed the message, and will need to email her your username and explain you missed the message.
Once your email address is verified, you will be able to play backgammon online!