Org Admins can add properties to new members they create or to existing members by clicking on their name to edit. When setting up a new member or editing use the search feature to find and add properties that you want the user to access. After you start typing, a drop down list of matching properties will be displayed. Click on a property name and it will appear on the list below.
To learn more about Account Types and the privileges associated with managing properties and residents, see this article.