Use one of two ways to switch from one meeting to the next on a Surface Hub.
From the Call pane
Select the Call button, then choose See scheduled meetings. Select your meeting to join it. If the meeting wasn't originally scheduled as a Skype for Business meeting, you'll have the option to ask the meeting organizer to make it an online meeting. Or, just continue to use the Surface Hub.
From the Welcome screen
Be sure to save anything you want to keep, then select End session. Files from the session will be removed and a new Welcome screen will appear. Select the next meeting to join it.
If you want to save your work from a meeting, be sure to email the files to yourself or save them to a USB memory stick before selecting End session (learn more about saving your work). The Surface Hub will be cleaned up to help protect your privacy, so your content, account info, and other data won't be available to the next group of people using the Surface Hub, and you won't be able to recover your files.