fix readme link, describe how it works

README.md

@@ -3,4 +3,18 @@ WILDS Registry
 
 Registry of WILDS repositories.
 
-The registry is in: [registry.json][]
+The registry is in: [registry.json][registry.json]
+
+How it works locally for testing purposes:
+
+```
+pip install -r requirements.txt
+python code.py
+```
+
+How it works on GitHub Actions via the `.github/workflows/build.yml` file:
+
+- Install Python
+- Install python libraries
+- Run `python code.py`
+- Commit changed `registry.json` file to the default branch (`gh-pages`). This updated file is then available at <https://getwilds.org/registry/registry.json>