Add note about configuring the CLI via environment variables

README.md

@@ -11,3 +11,24 @@ uses: dopplerhq/cli-action@v1
 ```
 
 You can see a live example of this Action [here](https://github.com/DopplerHQ/cli/blob/master/.github/workflows/cli-action.yml).
+
+## Configuration
+
+In most cases, you'll need to provide the CLI with an auth token. You can do so via the `DOPPLER_TOKEN` environment variable. In the below example, the token is retrieved from [GitHub secrets](https://docs.github.com/en/actions/security-guides/encrypted-secrets).
+
+```yaml
+name: Example action
+
+on: [push]
+
+jobs:
+  my-job:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Install CLI
+      uses: dopplerhq/cli-action@v1
+    - name: Do something with the CLI
+      run: doppler secrets --only-names
+      env:
+        DOPPLER_TOKEN: ${{ secrets.DOPPLER_TOKEN }}
+```