First, run your backend server. Please refer to the metal-pay-connect-nodejs-examaple.
Add your REACT_APP_BACKEND_API_BASE_URL to your .env file. If you are runnning it locally, this is most likely http://localhost:3005 because we set the backend example to default to that. You can also refer to our .env.example. If you are using typescript, you may also want to add REACT_APP_BACKEND_API_BASE_URL: string to your env.d.ts file.
npm install
npm run dev