Click on the Sharing link on the top right of Starkit. You will see a list of all users in your organization.
You can choose with who you like to share your email with. For each user you can click one of the two links available to allow Full Access or Read Only Access. Full Access will enable a Contact to have the same access to your emails as you do (Send/Receive) while Read Only means that he/she can read your emails but not send or reply to an email.