There are a number of actions you can take to ensure that an Employee is unable to access your account
If the Employee logs in with their own Employee ID:
You can change their password and revoke their logged in sessions. This will immediately terminate any current sessions that the Employee is logged into and disable them from being able to log back in.
Go to Manage > Employees > List and click on the Reset Password (padlock) icon for the Employee
Change their password & do not select the Send Email checkbox, but do select the Revoke Sessions checkbox. See How do I reset an Employee’s password?
If the Employee logs in with the location ID and password:
You can change the location password and revoke all logged in sessions. This will immediately terminate any current location sessions that the are logged into, and disable anyone from being able to log back in with the old password.
Go to Account > Settings page and click on the Change Password button
Make sure to select the Revoke Sessions checkbox
You will then have to re-login on all of your devices with your new password. See How to I change my account (location) password or PIN?