Be sure that the receiving user already has an Artwin Live account and you know that user's e-mail address set in Artwin Live account settings.
Login to your Artwin Live account and click on "My Schedules" in the account menu at top of the page. Click on the "Edit" button of the schedule you want to share. Scroll down to "Members" and press "Add new user".
Enter the user's e-mail address and select the permission for that user. Click "Save schedule" at the top of the page to invite the user.
In the schedule settings of a particular schedule you'll see the active members in the "Members" part. You may "Remove" a user.
Users that have not accepted your invitation yet are listed in the "Add new user" page. You may "Cancel" the invitation.