How can I allow colaborators to push/pull images from/to my private reporitory

hi there,
I’ve added a collaborator to my private repository on docker hub, but it seems that he is not able to pull/push any images I have there.
I’ve already checked on Settings tab for my repository and juts the options “Make Public” and “Delete repository” are listed there.
Can anyone tell me how can I allow him this kind of access?