Add instructions in README

README.md

@@ -1,2 +1,25 @@
-# tencent-cloud-cdn-purge-cache
-Purge Cache for Tencent Cloud CDN
+# Tencent Cloud CDN Purge Cache
+
+This action purges cache for Tencent Cloud CDN via its Python SDK API.
+
+## Environment Variables
+
+To use this Github action, you need to set the following environment variable in your workflow:
+
+| Name | Description | Required |
+| --- | --- | --- |
+| SECRET_ID | your Tencent Cloud access token Secret ID | Yes |
+| SECRET_KEY | your Tencent Cloud access token Secret Key | Yes |
+| PATHS | paths to purge cache for, separated with comma `,` | Yes |
+| FLUSH_TYPE | `flush` (default) to purge only modified resources or `delete` to purge all | No |
+
+## Example Usage
+
+```yaml
+uses: keithnull/[email protected]
+id: example
+env:
+  SECRET_ID: ${{ secrets.SECRET_ID}}
+  SECRET_KEY: ${{ secrets.SECRET_KEY }}
+  PATHS: "https://example.com/foo/,https://example.com/bar/"
+```