diff --git a/README.md b/README.md
index a3e2968..0e14387 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,69 @@
 # Setup Redmine
 
 [![Build](https://github.com/hidakatsuya/action-setup-redmine/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/hidakatsuya/action-setup-redmine/actions/workflows/build.yml)
+
+This GitHub Action installs Redmine and sets up an environment to run tests. It is primarily aimed at providing an environment to run tests for Redmine plugins.
+
+## Usage
+
+```yaml
+- uses: hidakatsuya/action-setup-redmine@v1
+  with:
+    # Redmine repository to setup. Default is redmine/redmine.
+    repository: 'redmine/redmine'
+
+    # The branch, tag or commit to checkout. Default is master.
+    version: 'master'
+
+    # Database to use for testing. Available values are sqlite3, postgresql. Default is sqlite3.
+    databae: 'sqlite3'
+
+    # Ruby version to use for testing. See ruby/setup-ruby's ruby-version input for available versions.
+    ruby-version: ''
+
+    # Directory to setup Redmine. Default is the current directory.
+    path: '.'
+```
+
+See also [action.yml](./action.yml).
+
+## Example
+
+### Setting up [RedMica](https://github.com/redmica/redmica)
+
+```yaml
+- uses: hidakatsuya/action-setup-redmine@v1
+  with:
+    repository: 'redmica/redmica'
+    version: 'v2.4.2'
+    database: 'postgresql'
+    ruby-version: '3.2'
+```
+
+### Run a test for the Redmine plugin
+
+For example, you are developing the `redmine_hello_world` plugin on GitHub repository. To run a test for that plugin in GitHub Action, do the following:
+
+```yaml
+- uses: hidakatsuya/action-setup-redmine@v1
+  with:
+    ruby-version: '3.3'
+
+- uses: action/checkout@v4
+  with:
+    path: plugins/redmine_hello_world
+
+- run: |
+    bundle install
+    bin/rails redmine:plugins:test NAME=redmine_hello_world
+```
+
+## Versioning
+
+This action follows [the recommendations of GitHub Actions Versioning](https://github.com/actions/toolkit/blob/master/docs/action-versioning.md).
+
+## Releasing
+
+1. Make sure CI for main branch has passed
+2. Create a new release to publish to the GitHub Marketplace
+3. Make sure that the release workflow has passed
diff --git a/action.yml b/action.yml
index 65ed559..d96ed7f 100644
--- a/action.yml
+++ b/action.yml
@@ -4,22 +4,22 @@ author: hidakatsuya
 
 inputs:
   repository:
-    description: 'Redmine repository to setup.'
+    description: 'Redmine repository to setup. Default is redmine/redmine.'
     required: true
     default: 'redmine/redmine'
   version:
-    description: 'The branch, tag or SHEA of the repository to setup.'
+    description: 'The branch, tag or commit to checkout. Default is master.'
     required: true
     default: 'master'
   database:
-    description: 'Database to use for testing. Available values are sqlite3, postgresql.'
+    description: 'Database to use for testing. Available values are sqlite3, postgresql. Default is sqlite3.'
     required: true
     default: 'sqlite3'
   ruby-version:
     description: "Ruby version to use for testing. See ruby/setup-ruby's ruby-version input for available versions."
     required: true
   path:
-    description: 'Directory to setup Redmine.'
+    description: 'Directory to setup Redmine. Default is the current directory.'
     required: true
     default: '.'