To add a collaborator, click theSharebutton at the top of the page while viewing the webmix in your workspace.
Next, click the green button toInvite a Collaboratornear the bottom of your share options.
Enter a name and e-mail address to invite a Collaborator. Edits made by you or your Collaborator(s) are shown in real-time. However, you may still need to 'Publish' your webmix to make the changes visible in your public workspace.
Watch the following video on how to add and collaborate on a webmix: