diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index cec91b3..4a4950e 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -48,8 +48,8 @@ jobs:
           INPUT_WHO_TO_GREET: Mona Lisa Octocat
         run: |
           docker run \
-            --rm ${{ env.TEST_TAG }} \
-            ${{ env.INPUT_WHO_TO_GREET }}
+            --env INPUT_WHO_TO_GREET="${{ env.INPUT_WHO_TO_GREET }}" \
+            --rm ${{ env.TEST_TAG }}
 
   test-action:
     name: GitHub Actions Test
diff --git a/README.md b/README.md
index adb15fb..a8b8b90 100644
--- a/README.md
+++ b/README.md
@@ -51,11 +51,20 @@ need to perform some initial setup steps before you can develop your action.
 
 1. :white_check_mark: Test the container
 
-   You can pass input arguments in the `docker run` call.
+   You can pass individual environment variables using the `--env` or `-e` flag.
 
    ```bash
-   $ docker run actions/container-action "Mona Lisa Octocat"
+   $ docker run --env INPUT_WHO_TO_GREET="Mona Lisa Octocat" actions/container-action
+   ::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
+   ```
 
+   Or you can pass a file with environment variables using `--env-file`.
+
+   ```bash
+   $ cat ./.env.test
+   INPUT_WHO_TO_GREET="Mona Lisa Octocat"
+
+   $ docker run --env-file ./.env.test actions/container-action
    ::notice file=entrypoint.sh,line=7::Hello, Mona Lisa Octocat!
    ```
 
@@ -76,12 +85,13 @@ can choose any base Docker image and language you like, you can change this to
 suite your needs. There are a few main things to remember when writing code for
 container actions:
 
-- Inputs are accessed using argument identifiers. For example, the first input
+- Inputs are accessed using argument identifiers or environment variables
+  (depending on what you set in your `action.yml`). For example, the first input
   to this action, `who-to-greet`, can be accessed in the entrypoint script using
-  `$1`.
+  the `$INPUT_WHO_TO_GREET` environment variable.
 
   ```bash
-  GREETING="Hello, $1!"
+  GREETING="Hello, $INPUT_WHO_TO_GREET!"
   ```
 
 - GitHub Actions supports a number of different workflow commands such as
diff --git a/action.yml b/action.yml
index 3cbcd3d..6a12f41 100644
--- a/action.yml
+++ b/action.yml
@@ -17,5 +17,5 @@ outputs:
 runs:
   using: docker
   image: Dockerfile
-  args:
-    - '${{ inputs.who-to-greet }}'
+  env:
+    INPUT_WHO_TO_GREET: ${{ inputs.who-to-greet }}
diff --git a/entrypoint.sh b/entrypoint.sh
index 42e39ea..22c9865 100755
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -1,7 +1,7 @@
 #!/bin/sh -l
 
 # Use INPUT_<INPUT_NAME> to get the value of an input
-GREETING="Hello, $1!"
+GREETING="Hello, $INPUT_WHO_TO_GREET!"
 
 # Use workflow commands to do things like set debug messages
 echo "::notice file=entrypoint.sh,line=7::$GREETING"