Directions vary depending on what you’re doing, but for a React app this will work.
So click on the actions tab in the repo, and click the nodejs template.
Change the run command to the npm script you want to run like npm run ci-check. It will do something along the lines of npm ci && npm run lint-check && npm run format-check && npm run test && npm run build.
Save that. Then move it from the repo root into a new subdirectory you’ll need to create called .github/workflows.
If you are an admin, click the settings tab and protect your merge branch so you can only merge if this succeeds.
That’s it!