After exporting your code you'll want to consult the README.md file in the root of your codebase for the instructions on deploying, as this can differ a bit depending on your chosen stack options.
Here's how you'd run your app if you selected the default stack (React and Vercel):
Install the Vercel CLI
npm install -g vercel
Add each variable from your
.env file to your Vercel project, including the ones prefixed with "REACT_APP_". You'll be prompted to enter its value and choose one or more environments (development, preview, or production). See Vercel Environment Variables to learn more about how this works, how to update values through the Vercel UI, and how to use secrets for extra security.
vercel env add plain VARIABLE_NAME
Run this command to deploy to a unique preview URL. Your "preview" environment variables will be used.
Run this command to deploy to your production domain. Your "production" environment variables will be used.