It depends on which permissions are assigned to your user ID. Should you have the required permissions needed to access any accounts but your primary one, you can view these accounts by going to the Login Gateway. The Login Gateway is the second section appearing on the Account Network homepage that is only viewable after you are part of an account network.
Click on the Login Gateway section and, if you have the appropriate permissions, you will see a blue Login button appearing to the right of any secondary account information in this section which, when clicked, will direct you to the main dashboard for that account.
To return to your primary account, re-enter the Account Network homepage through the Account ID menu at the top right corner of your screen. You will see a blue Back to My Account button below the Login Gateway header that you can click to return to your primary account.
Please note: You cannot access accounts that belong to a different account network from the one you're in. The only accounts a user can access are those that belong to the same account network.