Add your Twitter handle to the text box below and click "Update". If you have not yet followed the private feed, make sure you do before entering your handle below. Make sure the handle is not your name, rather it is the name following the "@" symbol on your account. See where "handle" is in the image below.
Make sure that your employee already has an account using the provided email. If not, have them sign up first by clicking "Create Account" at the bottom of any page. Once you've added an employee, they cannot be removed for at least 1 month.
Here you can see all of the employees currently on your plan. Clicking on the Trash icon will remove an employee from your Professional plan.