Sharing a map
The Premium plan lets you hand over some or all of the administration of a map to other people, without sharing your account credentials.
Inviting a collaborator
From your list of maps, click the "Share" button on the map in question, then enter the email address of the person to invite. They receive an email inviting them to create an account (if they don't already have one) and access the map.
Access levels
An access level is assigned to each invited person. The "View only" level grants read-only access to the map's administration, without the ability to modify it.
info
Other access levels, granting editing rights, are available in the interface; this page will be completed once their exact behavior has been documented.