Whilst you can perform most user administration from your own login, there are some operations that you need to do whilst acting as the sub-organisation such as managing groups, resources or permission sets for their account holders.
To impersonate a sub-organisation there are two approaches:
From the organisation list button at the top of the page:
This will give you a list of the organisations below you and next to each will be an impersonate button ( ):
From any search result
If your search results include accounts on the organisation tab, you will see the same impersonate button next to the usernames there.
From an organisation's account details page
From any organisation details page there will be an impersonate button in the top right:
All methods take you to the dashboard of the impersonated organisation.
The breadcrumb just below the menu will show you as acting as this organisation until you decide to return to acting as yourself or log out.
Clicking on the home icon or the OpenAthens logo at the top of the page takes you to the dashboard of the impersonated organisation rather than your own. To return to acting as yourself, click your own username in the breadcrumb.
For any organisations you regularly impersonate you can bookmark their homepages for easy access.