Add contribution workflow and synopsis

CONTRIBUTING.md

@@ -15,13 +15,81 @@ Please read the rest of this document to ensure a smooth contribution process.
 * [GitHub Flow Guide](https://guides.github.com/introduction/flow/):
   step-by-step instructions of GitHub Flow
 
-## Contributing to Issues
+## Issues for new contributors
 
 * Check if the issue you are going to file already exists in our [GitHub issues](https://github.com/powershell/DSC/).
 * If you can't find your issue already,
   [open a new issue](https://github.com/PowerShell/DSC/issues/new/choose),
   making sure to follow the directions as best you can.
 
+## Contribution Workflow
+
+Whether you’re fixing bugs, developing new functionality, or improving tests,
+contributions are managed through a GitHub-centered workflow.
+After setting up your GitHub account, follow these instructions:
+
+1. Fork the repo you plan to work on.
+
+   In GitHub, click Fork on the project page to create your copy under your account.
+
+1. Clone your fork locally
+
+   ```powershell
+   git clone https://github.com/<your-github-username>/DSC.git
+   cd DSC
+   ```
+
+1. Add the upstream remote and sync main
+
+   ```powershell
+   git remote add upstream https://github.com/PowerShell/DSC.git
+   git fetch upstream
+   git checkout main
+   git pull --ff-only upstream main
+   ```
+
+1. Create a new branch to hold your work.
+
+   ```powershell
+   git checkout -b <short-description>
+   ```
+
+1. Work on your new code. Write tests
+
+   ```powershell
+   ./build.ps1 -Clippy -Test
+   ```
+
+   The build script uses crates.io by default.
+   For prerequisites, test groups, and cross-platform builds,
+   see [Building and testing](#building-and-testing).
+
+1. Commit your changes with a clear message
+
+   ```powershell
+   git add -A
+   git commit -m "<concise summary of the change>"
+   ```
+
+1. Push your branch and open a Pull Request
+
+   ```powershell
+   git push -u origin <short-description>
+   ```
+
+   In GitHub, open a PR from your branch to the upstream main branch. Link related issues
+   and include a brief summary and rationale.
+   See [Pull Request Guidelines](#pull-request-guidelines).
+
+1. Keep your branch up to date
+
+   ```powershell
+   git fetch upstream
+   git rebase upstream/main
+   # resolve conflicts if any, then continue the rebase
+   git push --force-with-lease
+   ```
+
 ## Contributing to Documentation
 
 ### Contributing to documentation related to DSC