I want a user to be logged out automatically when they are not using the CRM. How can I set this up?

You can set this up in Vtiger CRM by specifying the period after which a user must be logged out automatically if there is no activity. 

Follow these steps to specify the logout time interval:

1. Log in to your CRM account.
2. Click the User Menu on the top right corner of the CRM screen.
3. Click Settings.
4. Look for the User Management section.
5. Select Authentication.
6. Click the Edit icon on the top right corner of the page.
7. Go to the Logout Policy section.
8. Select the time after which a user must be logged out from the Inactive Session Logout Interval drop-down.
9. Click Save.

Users are logged out of their sessions after the specified period irrespective of what device the session is running on.