You can add multiple accounts to the authenticator app, you need the seed (image or url) for each account that google gives you once when you first setup 2fa for that account. If you lose it and need it again, you have to turn off and turn on 2fa and then you'll get a new seed/image and new list of backup codes. So you might want to securely save those images/seed URLs when you first setup 2fa for each google account. Basically the same as how you are going to securely save the list of backup codes.
Or as gfunkdave suggested in another thread, you can use Authy instead which saves the seeds in the cloud so it can be shared amongst several devices running the authy app. (or 1password also does allows does it, if you are already using 1password.) Both authy and 1password (and I'm sure there's other apps as well) implement the same algorithm that the google authenticator app implement, so any of these can be used to generate the unique 2fa code given the seed image or url.
Personally I do all this in 1password, which shares it's database across all my devices and computers. Most people here seem to be fans of lastpass, so I guess they end up using Authy instead.
-David
Last edited by LIH Prem; Dec 4, 2016 at 9:05 pm