If your email address is used with multiple accounts, even across different domains, you can use the switch account feature to easily navigate between them.
Login in with your credentials in Campaign Manager or Location Manager.
Enter your one-time code
In the top right hand corner navigate with your cursor to your username.
Select 'Switch account'
You will be redirected to a page where you can switch between your accounts.
Click on your username.
From the list that appears select the desired account and press submit
Press 'Submit'
You will be redirected and are now logged in as the user that was selected.