LTPopUpReward *test = [[LTPopUpReward alloc] init];
UIPopoverController *popover = [[UIPopoverController alloc] initWithContentViewController:test];
CGFloat fltHeight = [UIScreen mainScreen].bounds.size.height;
CGFloat fltWidth = [UIScreen mainScreen].bounds.size.width;
popover.popoverContentSize = CGSizeMake(fltWidth/2, fltHeight/2); //your custom size.
CGRect rectPopUpReward = CGRectMake(500, 500, fltWidth/2, fltHeight/2);
[popover presentPopoverFromRect:rectPopUpReward inView:self.view permittedArrowDirections: UIPopoverArrowDirectionAny animated:YES];