If you want to use a domain with your Droplet, it's really easy; you need to change the Nameservers of your domain to point to Digital Ocean ones. For example, I have a domain, called educnow.com, which I'm going to use for my Droplet. I registered this domain with Godaddy, so I have to go to the domain management and select it. You can go directly to the https://dcc.godaddy.com/manage/YOURDOMAIN.COM/dns URL. Then go to Nameservers:

We have to click on the Change button, select Custom, specify the Digital Ocean Nameservers, and click on Save:

Once you've modified your Nameservers, you need to go to your Droplet dashboard and choose the Add a domain option:

Then introduce the domain you want to link to your Droplet and click on Add Domain:

Now you need to create a new record for CNAME. Select the CNAME tab, in the hostname write www, in the alias field write @, and by default the TTL is 43200—this is to be able to access your domain using the www.yourdomain.com prefix:

If you did everything correctly, you should be able to access your domain and see your React Application working; this process can take from 30 minutes to 24 hours depending on the DNS propagation speed.