Generally, you can access only a single gmail account in a browser at the same time. It’s quite troublesome to sign out one and login another.
Here is a small trick which enables you to login/access two or more gmail accounts.
1. First go to this Link and Login with your gmail account.
2. Click on Edit at “Multiple sign-in”
3. Select “On – Use multiple Google Accounts in the same web browser”. Then also select the check boxes.
4. Then Click on “Save”.
5. Now to add other gmail account see at top right for a arrow mark near your current gmail address, Click on that and click “Sign in to another account…”.
Have Fun !!