Assuming you've started the free trial - go to your Team page, type the email into "Add new employee by email" box and press Invite button.
The new employee would receive an email asking them to sign in into with the email you've typed. Once they do - they become a part of your team and are able to track time for your company.
What if an employee has not received an email? There's no need to "invite again" or resend the email - that email is optional. What important is the email address. Just ask the employee to sign up with that email and you will see them on your team.

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