You can create custom dataset class by inherting pytorch's torch.utils.data.Dataset.
The assumption for the following custom dataset class is 
| filename | 
label | 
| 4325.jpg | 
cat | 
| 2345.jpg | 
dog | 
 
- All images are inside 
images folder. 
class CustomDataset(torch.utils.data.Dataset):
    def __init__(self, csv_path, images_folder, transform = None):
        self.df = pd.read_csv(csv_path)
        self.images_folder = images_folder
        self.transform = transform
        self.class2index = {"cat":0, "dog":1}
    def __len__(self):
        return len(self.df)
    def __getitem__(self, index):
        filename = self.df[index, "FILENAME"]
        label = self.class2index[self.df[index, "LABEL"]]
        image = PIL.Image.open(os.path.join(self.images_folder, filename))
        if self.transform is not None:
            image = self.transform(image)
        return image, label
        
Now you can use this class to load the training and test dataset using both csv file and image folder.
train_dataset = CustomDataset("path - to - train.csv", "path - to - images - folder"  )
test_dataset = CustomDataset("path - to - test.csv", "path - to - images - folder"  )
image, label = train_dataset[0]