To access Business App as an admin, go to Partner Center > Businesses > Accounts > Account Name >Open in and select Business App.
This will open Business App for the account you selected. In Business App, admins will be able to navigate it just as a user would, but there are some key differences:
Admins will not be restricted to the tabs and products any particular user is restricted to. Should the admin wish to see Business App in the same way as a specific user, we recommend using the impersonate option.
This is done from Partner Center > Businesses > Users.
Admins can access any account they have access to in Partner Center using the location switcher in the top-left of Business App.