This article outlines how to set these fields:
TargetEntity["createdon"] = new DateTime(2011, 8, 8);
TargetEntity["overriddencreatedon"] = new DateTime(2011, 8, 8);
TargetEntity["createdby"] = new EntityReference("systemuser", new Guid("DDF26A49-4CBA-E311-9400-001CC4EECDD6"));
TargetEntity["modifiedby"] = new EntityReference("systemuser", new Guid("F1F26A49-4CBA-E311-9400-001CC4EECDD6"));
TargetEntity["modifiedon"] = new DateTime(2012, 8, 8);
Without custom code, you can use the overriddencreatedon field to set the CreatedOn when you create a record, but modifying the rest of the fields require the techniques described in the article.