There are a couple of different ways to get to a Live Room:
Join a Live Room From an Email Invite
When you are added to a Live Room, you will receive an email notification inviting you to the room. For every Live Room you're added to, you'll receive a separate invitation.
You can access that room directly from the link in the email invite.
Join a Live Room Within CORE's Live Rooms Space
If you're logged in CORE and your default settings don't immediately take you to your Live Rooms space, access it by selecting the Streaming icon in the left hand menu.
Hovering over the icon on your desktop will expand the menu to show what feature it is:
Select the icon to be taken to your Live Rooms. If you have access to more than one room, they will all appear here. To join the room, select the thumbnail.
With the latest build of Live Rooms, active rooms are highlighted in green as seen below.