Permissions over Model elements within a Model are allocated to individual Users within a Project, and to a Group of Users within a Group.
NB Group Permissions supersede User level Permissions within a Project.
NB Permissions supersede Function allocations within the Role/s played by a User on a Project.

There are five types of Permissions, Full Rights, Create, Read, Alter and No Permission.

For instance, you may include a User within a Project, and for each Model allocated to that Project a User may be granted only Read Permission. I.e. That User can view the Model, but not alter/edit the Model. You may also stipulate that a User has Full Rights or No Permissions at all over Models within a Project.

The Permissions of a User within a Project, for instance, can be viewed and edited by clicking on the name of the User within the list of Users included within a Project.