Workflow configuration steps - Groups association to workflow
This form/tab enables to define the groups which can be used to assigned workflow privileges for. Privileges can be, for example, performing a workflow transition or viewing/updating a workflow field.
Just select and add to this tab the groups you want to use. Remember, that adding groups is just an enabling step. Actual configuration of privileges is done in the other workflow configuration forms/tabs. However, if you don't enable groups here you won't be able to set privileges relating to them for the workflowelsewhere.