Based on assumption that you already finished working on your react project. There are several platforms used in deployment. I’m using vercel for this tutorial not because it’s ..well, a vercel deployment tutorial.
Vercel assumes that you are working on the master branch so it’s kind of a big deal to always use master as the main branch.
Head over to https://vercel.com/login and Continue with github (recommended). You should be redirected to Vercel Overview.
Select New Project on Import Project, then Continue, paste your git repository URL, continue and if everything went accordingly, the rest of the steps are pretty obvious.