Yes, this is possible and can be easily accomplished through the app. If you would like to add a user, go to Settings ->User management in your Remarekty dashboard.
In the User management page, plug in the email address of the contact you wish added, and click on the "send invitation" button.
If something unexpected occurred and the invitation was not sent correctly, please send his or her information to firstname.lastname@example.org in the format below:
Subject: Add user to Store Name
We will be sure to add the user as soon as possible.