Restoring an archived lead will move it back to the same stage in the pipeline from where it was archived. If that stage has been deleted, then it will move it back to the first stage in the pipeline.
All the information pertaining to the lead which was archived along with the lead will still be present once its restored. It will also be assigned to the same user it was assigned before it was archived.
To restore an archived lead click on the option Archived Leads from the top menu.
Click on the Restore Lead button