To add a new account to your group, go to your Group Dashboard. The top row of buttons will allow you to add a new user. To do so, click on the button 'Add User':
On the following page, you'll be able to create the address of the account you would like to set up. The page is the same page for adding a new account. Enter the first part of the address you want to include. If you want to select a Pobox domain, such as @pobox.com or @foobox.com, you can click on the dropdown box that shows 'pobox.com'. If you have your own domain, you can click on the blue link 'use your own domain':
After selecting the domain for the new address, you'll be given an option to add the address to your address, or a new account. Click on the 'A New Account' button:
The final set of options will allow you to set up the specifics of the account. First, choose if you want to pay for the account, which means it would be in your billing group and show up when you have an invoice.. Second, choose the type of account you want to create, Mailstore, Plus, or Basic. Next, choose the forwarding address for the account.
Next, enter the First/Last name of the user, and the password for the account. Finally, choose if you want to be the admin for the account, and if your new account can create addresses at a custom domain you that is on your 'admin' account.
If you want to be administrator, leave that box selected. If you want to allow this account to use your custom domains, leave that box selected:
To finish, click on the green 'Create Account' button.