Placing a margin around each edge of the UICollectionView

You can make use of the following function.

- (UIEdgeInsets)collectionView:(UICollectionView *)collectionView layout:(UICollectionViewLayout*)collectionViewLayout insetForSectionAtIndex:(NSInteger)section
  {
      return UIEdgeInsetsMake(50, 50,15,50);
  }

You will have to play around with the number to figure out how to force the collectionviewCells in a single line.

UIEdgeInsetsMake ( CGFloat top,CGFloat left,CGFloat bottom,CGFloat right); 

For Swift 3

func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
    return UIEdgeInsetsMake(10, 4, 10, 4)
}

I know this is an old question, but don't forget that UICollectionView inherits from UIScrollView.

UICollectionView *collectionView = [[UICollectionView alloc] init];
collectionView.contentInset = UIEdgeInsetsMake(x.x, x.x, x.x, x.x);

// Swift 3 for good measure
let collectionView = UICollectionView()
collectionView.contentInset = UIEdgeInsets(top: x.x, left: x.x, bottom: x.x, right: x.x)

Be aware that both contentInset and sectionInset may change the spacing of cells in your view. For more information on that, see this post.