Where to add DataParallel

I am trying to run the following code with multiple GPUs but I am not getting where to add the following?

net = torch.nn.DataParallel(model, device_ids=[0, 1, 2])

with torch.cuda.device(CUDA_VISIBLE_DEVICES):
                if args.dataset == "fashionmnist":
                    resnet18    = resnet.ResNet18fm(num_classes=NO_CLASSES).cuda()
                    #resnet18    = vgg11().cuda() 
                    resnet18    = resnet.ResNet18(num_classes=NO_CLASSES).cuda()
                if method == 'lloss':
                    #loss_module = LossNet(feature_sizes=[16,8,4,2], num_channels=[128,128,256,512]).cuda()
                    loss_module = LossNet().cuda()

            models      = {'backbone': resnet18}
            if method =='lloss':
                models = {'backbone': resnet18, 'module': loss_module}
            torch.backends.cudnn.benchmark = True
            models = torch.nn.DataParallel(models, device_ids=[0])