In the sidebar on the left side of your screen click on the "Organization" link or icon. You will see a few options for interacting with your organization's members.
When sending invites, there are some rules that apply. You may only invite users to participate at a level below you.
The order is Owner > Clinic > Member. This means an Owner may invite both Clinics and Members to join. A Clinic may invite only Members.
DO NOT modify these details if you are not the project owner.