Update CONTRIBUTING.md

adding tips of contributing

CONTRIBUTING.md

@@ -36,3 +36,15 @@ You can then [open a pull request][pr] on [the l10n repository][l10n].
 [l10n]: https://github.com/mozilla-l10n/multi-account-containers-l10n/
 [pr]: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests
 [web-ext]: https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Getting_started_with_web-ext
+
+##Tips for contributing:
+
+* Choose an issue from https://github.com/mozilla/multi-account-containers/issues that you would like to work on.
+* Fork the repository and follow the instructions for setting it up locally.
+* Run the add-on locally and try reproducing the issue.
+* Debug add-ons by clicking the “Settings” icon in about:addons, and then clicking “Debug Add-ons”
+* Click “Inspect” on the MAC add-on to open developer tools for the popup extension (see https://extensionworkshop.com/documentation/develop/debugging/ for more information)
+* Once you have a fix ready, commit your changes with the following template
+* “Fix #<insert issue id #>: <description>”
+* Push your changes and open a pull request for review.
+