You can find the "Your organisation" page in the fourth section (Settings) of the main navigation menu at the left of the window. (You may see more options in the menu if you are, for example, an organisation admin.)
Click the second option ("Your organisation") to go to your organisation page.
The Your Organisation page has two areas. First, the existing users.
The first table is the list of people who currently have access to your organisation in Umbrella. For each person, you can see their name, email address, whether they're an organisation admin, any tags that have been assigned to them, when they last used the Umbrella platform, and when they originally signed up.
If you click on any row in this table, you'll be taken to their profile page, where you can see further information, including a log of their recent activity.
Below this (or on the right if your window is wider) there are statistics on your organisation: how many people have joined the team on Umbrella and how active they've been. Under this is a timeline showing the users who have been active most recently and what their last action was.