If you are a collaborator to a makey, you have admin rights to add another person as a collaborator to a makey. Others can make one off contributions to your makey without being a collaborator. Being a collaboration give you editorial and admin rights. Here is how you can add a collaborator to your makey.
Make sure that the new collaborator is signed up on Makeystreet.
On your makey page click on "settings" button on the top right