Update README.md

README.md

@@ -13,9 +13,15 @@ $ pip install hdxms-datasets
 
 
 ```python
+from pathlib import Path
 from hdxms_datasets import DataVault
 
-vault = DataVault()
+# local path the download datasets to
+
+cache_dir = Path('.cache')
+
+# create a vault with local cache dir, set `remote_url` to connect to a different database
+vault = DataVault(cache_dir=cache_dir)
 
 # Download a specific HDX dataset
 vault.fetch_dataset("20221007_1530_SecA_Krishnamurthy")