if we select Designated user then task will be assigned to that user inbasket

Hi, Please help me. I have linked the workflow to part item. When i am creating the new item in the part i have selected user in designated user field type. But i did not get any task. Usually when we select the designated user in the part form while creation of item then task to should come to MyInbasket for the user which we have selected in the designated user field type. other wise we should mention in the workflow itself?