When adding a new coach, you have the option of sending an invitation immediately.
You can also invite the new coach at a later time. Doing so allows you to configure pairing and permissions in advance. When you're ready to invite the new coach, do so through the Invite button (next to Pairing).
Feel free to edit the invitation email. You can edit the default email through the Settings tab >> System >> Message Templates. Click Send Invitation to send the email invite.