First get the parameters of your model as a vector
from torch.nn.utils import vector_to_parameters, parameters_to_vector

param_vector = parameters_to_vector(model.parameters())

Then sample a gaussian noise of the same size as this vector and add it.
n_params = len(param_vector)
noise = Normal(0, 1).sample_n(n_params)
param_vector.add_(noise)

Finally, load the parameters back to your model.
vector_to_parameters(param_vector, model.parameters())