You have to edit you provisioning profile in iOS provisioning portal. Select "edit" button and then "Modify". Enter the required info (your name, devices, appl. id).
When the system shows that the profile is "Active", go to Certificates section of the iOS provisioning portal and check your development certificate. It should have your provisioning profile listed in the "Provisioning Profile" entry.
After then, you can download the profile and drop it into Xcode.