Update README (#24)

Author: timctho

README.md

@@ -56,6 +56,10 @@ You can run this repo virtually by using GitHub Codespaces, which will open a we
 1. Go to `Access Control (IAM)` in resource, grant yourself role `Cognitive Services User`
 1. Copy `notebooks/.env.sample` to `notebooks/.env`
 1. Fill **AZURE_AI_ENDPOINT** with the endpoint from your Azure portal Azure AI Services instance.
+1. Login Azure
+   ```shell
+   az login
+   ```
 
 ## Open a Jupyter notebook and follow the step-by-step guidance