If the Designation you need to assign to your staff is not available then you may need to add a designation (or Job Assignment) to your available list.
Settings > Facility > Organization > Manage Organization Unit and then click on Long Term Care
From here you can add a Position or click on a current position to edit it.
From here you can add the new position as well as where this position Reports To, a Provider Group/Type and also assign it to a specific system Postion Role. Once you have added the new position click on Done.
Once you have clicked on Done make sure you also click Save on the next screen.
Now that your new position has been added it will be available to be set as a designation to your staff.
For instructions on how to set a designaion please see this article: https://medecare.zendesk.com/entries/22069662