The "Inbox" is going to be your main base of operations when it comes to seeing active 911 calls. You will still receive the standard notification when the app is not open as well as a notification when looking at the app. In addition is when you are using other features within the app you will see the inbox turn red and numbers will appear, letting you know there are new messages or calls waiting to be viewed and acted upon. 

As you can see by the two screenshots above, your inbox becomes red and alerts you as to how many new calls have come in since last viewing it. Once you tap the Inbox icon you will see those active calls and act from there. 

If there is a call you'd like to view on the map all you need to do is tap &hold on the particular call in the inbox and it will bring you to its location on the map. As seen below. 

Then you will simply tap the call you just selected either from the map or in the inbox for more information as seen below.

NOTE: the object mini-menu (which is where you see "Details", "Near by" and more) can be expanded by tapping that down arrow. Like so.