Add training and test descriptions

configs/restorers/tdan/README.md

@@ -23,3 +23,43 @@ The metrics are `PSNR / SSIM`.
 |:-------------------------------------------------------------------:|:---------------:|:---------------:|:---------------:|:---------------:|:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------:|
 | [tdan_vimeo90k_bix4](/configs/restorers/tdan/tdan_vimeo90k_bix4.py) | **26.49/0.792** | **30.42/0.856** |   25.93/0.772   |   29.69/0.842   | [model](https://download.openmmlab.com/mmediting/restorers/tdan/tdan_vimeo90k_bix4_20210528-739979d9.pth) \| [log](https://download.openmmlab.com/mmediting/restorers/tdan/tdan_vimeo90k_bix4_20210528_135616.log.json) |
 | [tdan_vimeo90k_bdx4](/configs/restorers/tdan/tdan_vimeo90k_bdx4.py) |   25.80/0.784   |   29.56/0.851   | **26.87/0.815** | **30.77/0.868** | [model](https://download.openmmlab.com/mmediting/restorers/tdan/tdan_vimeo90k_bdx4_20210528-c53ab844.pth) \| [log](https://download.openmmlab.com/mmediting/restorers/tdan/tdan_vimeo90k_bdx4_20210528_122401.log.json) |
+
+
+## Train
+
+You can use the following command to train a model.
+
+```shell
+./tools/dist_train.sh ${CONFIG_FILE} ${GPU_NUM} [optional arguments]
+```
+
+TDAN is trained with two stages. For example, when training on Bicubic downsampling, you need to use
+
+
+```shell
+./tools/dist_train.sh configs/restorers/tdan/tdan_vimeo90k_bix4_lr1e-4_400k.py 8
+```
+
+followed by
+
+```shell
+./tools/dist_train.sh configs/restorers/tdan/tdan_vimeo90k_bix4_ft_lr5e-5_400k.py 8
+```
+
+For more details, you can refer to **Train a model** part in [getting_started](/docs/getting_started.md#train-a-model).
+
+## Test
+
+You can use the following command to test a model.
+
+```shell
+python tools/test.py ${CONFIG_FILE} ${CHECKPOINT_FILE} [--out ${RESULT_FILE}] [--save-path ${IMAGE_SAVE_PATH}]
+```
+
+Example: Test TDAN on SPMCS-30 using Bicubic downsampling.
+
+```shell
+python tools/test.py configs/restorers/tdan/tdan_vimeo90k_bix4_ft_lr5e-5_400k.py  checkpoints/SOME_CHECKPOINT.pth --save_path outputs/
+```
+
+For more details, you can refer to **Inference with pretrained models** part in [getting_started](/docs/getting_started.md#inference-with-pretrained-models).