Sure!
Given your example target, you could use scatter to create the multi-hot target:
labels = torch.tensor([1, 4, 1, 0, 5, 2])
labels = labels.unsqueeze(0)
target = torch.zeros(labels.size(0), 15).scatter_(1, labels, 1.)
print(target)
> tensor([[1., 1., 1., 0., 1., 1., 0., 0., 0., 0., 0., 0., 0., 0., 0.]])

nn.BCEWithLogitsLoss takes the raw logits of your model (without any non-linearity) and applies the sigmoid internally.
If you would like to add the sigmoid activation to your model, you should use nn.BCELoss instead.