Вы можете определить CGRect, на который вы хотите указать поповер.
CGPoint point = ...; // where they tapped on screen, taken from UIEvent, if you like
CGSize size = ...; // give a size range, maybe the size of your table cell
[popover presentPopoverFromRect:CGRectMake(point.x, point.y, size.width, size.height)
inView:self.view permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];