This question has been answered by sottwell. See the first response.
It depends on what version of MODX you're running.Hi Bob, thans a lot for responding! I love your blog.
That's basic ACL configuration - if anything having to do with ACLs can be called "basic", anyway.
And, of course, BobRay has everything you need to know (and a lot more). http://bobsguides.com/creating-manager-users.html