add testing section

CONTRIBUTING.md

@@ -2,6 +2,23 @@
 
 Thank you for your interest in contributing to the 1Password install-cli-action project 👋! Before you start, please take a moment to read through this guide to understand our contribution process.
 
+## Testing
+
+After following the steps below for signing commits, you can test against your PR with these steps:\
+
+1. Create or use an existing repo to run the `install-cli` GitHub Action\
+2. In a workflow yaml file that uses the GitHub Action with
+
+   ```
+   uses: 1Password/load-secrets-action@<branch-name>
+
+   # OR
+
+   uses: 1Password/load-secrets-action@<commit-hash>
+   ```
+
+3. Trigger the action to test against your changes
+
 ## Documentation Updates
 
 If applicable, update the [README.md](./README.md) to reflect any changes introduced by the new code.