Finish README

README.md

@@ -1,5 +1,39 @@
 # action-fixme-alert
 
-Checks the code base for any `FIXME:` (with the colon) and fails the check if any are found.
+Checks the code base for any `FIXME:` (with the colon) and fails the check if any are found. Useful if you want to make sure that you don't miss any required changes in the code base before merging a PR.
 
-Useful if you want to make sure that you don't miss any changes in the code base before merging a PR.
+This uses the built-in `git grep` command, and the built-in [action problem
+matchers](https://github.com/actions/toolkit/blob/master/docs/problem-matchers.md),
+so it's very fast. It only takes a few seconds to run, even on a very large
+codebase.
+
+## Installation
+
+Edit or create a workflow `.yml` file in `.github/workflows` folder of your repository.
+
+Here's an example of a `linters.yml` workflow.
+
+```yml
+name: Linters
+
+on: [push]
+
+jobs:
+  fixmes:
+    name: FIXME check
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v1
+    - uses: bbugh/action-fixme-check@master # or @ the latest release
+```
+
+## Support
+
+- [Official workflow configuration docs](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions).
+
+## License
+
+The `action-fixme-check` library is available as open source under the terms of
+the [MIT License](http://opensource.org/licenses/MIT). This license means you
+can use it however you want, as long as you give me credit. Praise and adoration
+is optional, but encouraged.