Update README.md (#15)

Author: DrewProebstel

README.md

@@ -1,6 +1,73 @@
-## README
+# Prior Year Access – File Your State Taxes
 
-### How to compile sass files
-This repo uses the gem `dart-sass` to compile the .scss files. 
+This repository supports **Prior Year Access** for users of **File Your State Taxes**. It allows individuals who filed their state taxes with us in **2023** or **2024** to securely retrieve their tax return PDFs.
 
-To run this locally, use the command: `bin/rake dartsass:build`
+
+---
+
+## Infrastructure with OpenTofu
+
+This project uses OpenTofu to manage infrastructure as code. It provisions and maintains various cloud resources, including:
+
+- S3 buckets
+- EC2 instances
+- IAM roles
+
+The infrastructure for this repository is located in the [CFA Tax-Benefits-Backend repository](https://github.com/codeforamerica/tax-benefits-backend)
+  [Staging](https://github.com/codeforamerica/tax-benefits-backend/tree/main/tofu/config/staging.pya.fileyourstatetaxes.org)
+  [Production](https://github.com/codeforamerica/tax-benefits-backend/tree/main/tofu/config/pya.fileyourstatetaxes.org)
+
+### CI/CD Integration
+
+OpenTofu is integrated into our CI pipeline.
+---
+
+## Deployment to AWS Staging
+
+This project uses a GitHub Actions workflow to automatically deploy to the AWS staging environment after tests pass on the `main` branch.
+
+### Workflow Breakdown
+
+#### 1. Test Job
+
+- Runs the full Rails test suite:
+  ```bash
+  bin/rails db:test:prepare test test:system
+  ```
+- Sends test status notifications to Slack, tagging the appropriate team members
+
+#### 2. Deploy Job
+
+- Executes only if the test job completes successfully
+- Builds a Docker image and pushes it to Amazon ECR
+- Updates an AWS Systems Manager (SSM) parameter with the image tag to track the deployed version
+- Triggers a downstream GitHub Action in the [`tax-benefits-backend`](https://github.com/codeforamerica/tax-benefits-backend) repository using a `repository_dispatch` event, passing:
+
+  ```json
+  {
+    "environment": "pya-nonprod",
+    "config": "staging.pya.fileyourstatetaxes.org"
+  }
+  ```
+  The deploy job can be triggered manually by navigating to the github actions page and running the `Deploy to AWS Staging` action.
+
+### Environment Variables & Secrets
+
+The workflow relies on the following secrets:
+
+- `AWS_ACCESS_KEY` / `AWS_SECRET_KEY`: Credentials for accessing AWS services (ECR, SSM)
+- `SLACK_WEBHOOK_URL`: Sends Slack notifications for test results
+- `STAGING_DEPLOY_PAT`: GitHub Personal Access Token used to trigger the downstream deployment workflow
+
+  The staging PAT will need to be regenerated every 90 days and updated in Github and Lastpass
+---
+
+## Stylesheet Compilation
+
+This project uses the [`dart-sass`](https://rubygems.org/gems/dart-sass) Ruby gem to compile SCSS files.
+
+To compile stylesheets locally:
+
+```bash
+bin/rake dartsass:build
+```