Well there are a couple ways to do this. First off, make sure you have setup the second google account. Then while connected to the first one, click on the upper right icon RIGHT next to the grid of squares (those are the Google Apps), it might be your picture, OR whatever you choose as your avatar. You will see the option to Sign Out, or Add Account. You can Sign Out, then sign on to the other account each time, OR you can Add Account, and then be able to switch back and forth between the two by simply clicking on that icon again, and then you will see both, click on the one you want to use.