Input.unsqueeze(dim=1)
# or
Input.view(-1, 1, 2048)

If you want to use batches (assuming you’re using a data loader) you would write a collate function to pass to the loader which takes a batch and pads all of the sequences within the batch to the same length, adds them to a list then concatenates them on dim 1.
I’m not sure if the seq2seq tutorial was ever fixed to work with batches so you may have to make some other alterations. It’s quite old but there are plenty of seq2seq examples floating around github.