Hoping you have CUDA toolkit installed properly!
using this
device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")

net=model().cuda()

My laptop is core i5 with Geforce MX150 2GB and 4GB of RAM
on CPU it took a simple NN about 1min 58sec
on GPU it took 1 min 3sec, CPU usage is less than 50%