I have the same question. Getting nodejs going was straightforward, but I'm struggling with the reactjs portion. I was able to start reactjs like this:
yarn create react-app client
yarn start
A browser window opened. On a Plesk nodejs website it seems like nodejs has to take the lead fielding requests from browsers since it is a nodejs app that is the "Application Startup File". It must then somehow hand off requests to reactjs, but that seems backwards since reactjs is the frontend.