If you just want to use the GPU to train your model etc., you can simply push the data and model to your device using:
model.to('cuda')
data = data.to('cuda')
output = model(data)  # will be performed on the GPU

You don’t need to write CUDA code for it or would you like to implement a specific CUDA kernel for a method?
In that case, have a look at the GitHub issues 1 where you might find a good starter project.