Setting card permissions is just like setting any other Rule.

Global permissions

In addition to card permissions, the following global permissions can each be assigned to one or more Roles. Each accounts can, in turn, be assigned one or more roles, and has all of the global permissions that have been assigned to any of Role given to that account.

You will be able to set global permissions only if your account has the Administrator Role (which automatically has all three permissions).

• administrate users — the power to block Users, change their email address, and reset their passwords (all on their Options tab)
• create accounts — the power to give out accounts by approving requests (they must also be able to see Account Requests), and by adding accounts to existing cards
• assign user roles — the power to assign any Role to any User (using their Options tab). This is equally powerful to set global permissions, and should generally not be given to any role.

If you have the Administrator role, then at the bottom of the sidebar you will see an "Administrator links" card — which includes links to administrate accounts and roles, and to set these global permissions.